Requesting direction for installation problem
Hi, Where can one get assistance if a Windows installation service fails to install an msi installer? I used to download zip files, but they seem to have been replaced with msi files. I know this issue is off topic here. So my question simply is: where is it not off topic? Thanks for any hint Frederic -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Glenn Linderman wrote: > it appears the > OP understands that issue, and is asking why languages without > namespaces don't add them. Note that Xah Lee is not generally someone who (or something that) "asks" in order to learn something or to understand issues better. The more general interest appears to be spreading controversial topics over a vast number of newsgroups. Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: Reg Expression - Get position of >
"Chris Rebert" <[EMAIL PROTECTED]> wrote: > On Wed, Nov 26, 2008 at 1:48 AM, M_H <[EMAIL PROTECTED]> >> >> I have a beginning of a (longer) string who is like: >> mystr = '
Re: How to get a directory file descriptor?
alex23 wrote: > On Nov 26, 3:26 pm, greg <[EMAIL PROTECTED]> wrote: >> os.O_DIRECTORY must be fairly new -- it doesn't exist >> in my 2.5 installation. But os.O_RDONLY seems to work >> just as well for this purpose. > > Which OS are you using? > > Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52) > [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2 > Type "help", "copyright", "credits" or "license" for more information. import os hasattr(os, 'O_DIRECTORY') > True > > I'm pretty certain it was present under Windows XP as well. > > > -- > http://mail.python.org/mailman/listinfo/python-list > Hello, Thanks for your reply. I checked my Python 2.5 install on Linux and there's the O_DIRECTORY flag. However this is not mentioned anywhere in the Library Reference. There's another question regarding to this flag though: I checked the manual of the Linux system call open(2), in which there's a paragraph on this flag: O_DIRECTORY If pathname is not a directory, cause the open to fail. This flag is Linux-specific, and was added in kernel version 2.1.126, to avoid denial-of-service problems if opendir(3) is called on a FIFO or tape device, but should not be used outside of the implementation of opendir(3). Note the "should not be used outside of the implementation of opendir(3)" part. Does that mean using Python's os.open() with the O_DIRECTORY flag is a Bad Thing? In C, I think, calling opendir() followed by dirfd() should be the correct way of doing this? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Tkinter and asyncronous socket
Hi all, I'm new to python and I've been spending the last week on GUI that refresh its content based on data periodically coming from a remote socket. I succeded in doing it (thanks newsgroups and online manual!) using the Tkinter.after method to implement a busy wait on the socket (which I had previously set to non blocking) I should be happy with it, but on windows (application must be multi- platform) the busy wait leads to a 100% CPU usage. I'm trying to implement it the other way round: a "socket process" that updates a label (or a queue object) in the GUI. I can't figure out how to do this. Anyone can post hints? With some details, maybe? Thanks all Max -- http://mail.python.org/mailman/listinfo/python-list
Re: Python C/API simple debugging
k3xji wrote:
> I am new to Python C API and finding it difficult to debug C
> extensions. So, basically I want to see the value of an integer value
> during the C API. Here is the code:
>
> #define LAST_MIX_VAL 0xDEADBEEF
>
> static PyObject *
> chash(PyObject *self, PyObject *args)
> {
> unsigned int key,result; //treat key like an usinged int.
> unsigned char a,b,c,d;
>
> key = result = 0;
> if (!PyArg_ParseTuple(args, "i", &key))
> return NULL;
>
> printf("Key:%i\n",Py_BuildValue("i", key));
> .
> .
> [...]
> - What is the preffered approach for these kind simple-debugging
> issue?
If you want to simplify this kind of debugging as well as the general code
writing itself, consider using Cython.
http://cython.org/
Apart from that, I'd use gdb for debugging these things. It does have a
learning curve, but in change gives you a lot more than just "print-debugging".
Stefan
--
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Re: Python C/API simple debugging
On Nov 26, 1:34 pm, Stefan Behnel <[EMAIL PROTECTED]> wrote:
> k3xji wrote:
> > I am new to Python C API and finding it difficult to debug C
> > extensions. So, basically I want to see the value of an integer value
> > during the C API. Here is the code:
>
> > #define LAST_MIX_VAL 0xDEADBEEF
>
> > static PyObject *
> > chash(PyObject *self, PyObject *args)
> > {
> > unsigned int key,result; //treat key like an usinged int.
> > unsigned char a,b,c,d;
>
> > key = result = 0;
> > if (!PyArg_ParseTuple(args, "i", &key))
> > return NULL;
>
> > printf("Key:%i\n",Py_BuildValue("i", key));
> > .
> > .
> > [...]
> > - What is the preffered approach for these kind simple-debugging
> > issue?
>
> If you want to simplify this kind of debugging as well as the general code
> writing itself, consider using Cython.
>
> http://cython.org/
>
> Apart from that, I'd use gdb for debugging these things. It does have a
> learning curve, but in change gives you a lot more than just
> "print-debugging".
>
> Stefan
OK.
How to use gdb? I am compiling the extension to a "pyd" file and
importing it right now. So, I assume we need to, somehow load the
extension dynamically for debugging? But how?
Thanks
--
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Re: Python C/API simple debugging
k3xji wrote:
> On Nov 26, 1:34 pm, Stefan Behnel <[EMAIL PROTECTED]> wrote:
>> k3xji wrote:
>> > I am new to Python C API and finding it difficult to debug C
>> > extensions. So, basically I want to see the value of an integer value
>> > during the C API. Here is the code:
>>
>> > #define LAST_MIX_VAL 0xDEADBEEF
>>
>> > static PyObject *
>> > chash(PyObject *self, PyObject *args)
>> > {
>> > unsigned int key,result; //treat key like an usinged int.
>> > unsigned char a,b,c,d;
>>
>> > key = result = 0;
>> > if (!PyArg_ParseTuple(args, "i", &key))
>> > return NULL;
>>
>> > printf("Key:%i\n",Py_BuildValue("i", key));
>> > .
>> > .
>> > [...]
>> > - What is the preffered approach for these kind simple-debugging
>> > issue?
>>
>> If you want to simplify this kind of debugging as well as the general
>> code writing itself, consider using Cython.
>>
>> http://cython.org/
>>
>> Apart from that, I'd use gdb for debugging these things. It does have a
>> learning curve, but in change gives you a lot more than just
>> "print-debugging".
>>
>> Stefan
>
> OK.
>
> How to use gdb? I am compiling the extension to a "pyd" file and
> importing it right now. So, I assume we need to, somehow load the
> extension dynamically for debugging? But how?
You write a testscript that exposes the error you want to observe in the
C-layer.
Then you do
$ gdb python
# set args testscript.py
# break
# run
That pretty much is it. You can't single-step python code this way, but you
can walk through C/C++-code.
Diez
--
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Re: Python C/API simple debugging
On Nov 26, 1:43 pm, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote:
> k3xji wrote:
> > On Nov 26, 1:34 pm, Stefan Behnel <[EMAIL PROTECTED]> wrote:
> >> k3xji wrote:
> >> > I am new to Python C API and finding it difficult to debug C
> >> > extensions. So, basically I want to see the value of an integer value
> >> > during the C API. Here is the code:
>
> >> > #define LAST_MIX_VAL 0xDEADBEEF
>
> >> > static PyObject *
> >> > chash(PyObject *self, PyObject *args)
> >> > {
> >> > unsigned int key,result; //treat key like an usinged int.
> >> > unsigned char a,b,c,d;
>
> >> > key = result = 0;
> >> > if (!PyArg_ParseTuple(args, "i", &key))
> >> > return NULL;
>
> >> > printf("Key:%i\n",Py_BuildValue("i", key));
> >> > .
> >> > .
> >> > [...]
> >> > - What is the preffered approach for these kind simple-debugging
> >> > issue?
>
> >> If you want to simplify this kind of debugging as well as the general
> >> code writing itself, consider using Cython.
>
> >>http://cython.org/
>
> >> Apart from that, I'd use gdb for debugging these things. It does have a
> >> learning curve, but in change gives you a lot more than just
> >> "print-debugging".
>
> >> Stefan
>
> > OK.
>
> > How to use gdb? I am compiling the extension to a "pyd" file and
> > importing it right now. So, I assume we need to, somehow load the
> > extension dynamically for debugging? But how?
>
> You write a testscript that exposes the error you want to observe in the
> C-layer.
>
> Then you do
>
> $ gdb python
> # set args testscript.py
> # break
> # run
>
> That pretty much is it. You can't single-step python code this way, but you
> can walk through C/C++-code.
>
> Diez
OK I see your point, I just expected an another way to do that from
distutils itself. Thanks for the answer.
By the way for simple print-debugging, below works right now, I forgot
to try that
fprintf(stderr,"%d", key);
Thanks all again
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Re: Requesting direction for installation problem
Frederic Rentsch a écrit : Hi, Where can one get assistance if a Windows installation service fails to install an msi installer? I used to download zip files, but they seem to have been replaced with msi files. I know this issue is off topic here. So my question simply is: where is it not off topic? I'd have a look at the comp.os.ms-windows* hierarchy... -- http://mail.python.org/mailman/listinfo/python-list
[lambda]Is the behavior expected?
Hi all, def getFunc(x): return lambda y : x + y if __name__ == '__main__': todo = [] proc = getFunc(1) todo.append(lambda: proc(1)) proc = getFunc(2) todo.append(lambda: proc(1)) proc = getFunc(3) todo.append(lambda: proc(1)) todo.append(lambda: getFunc(1)(1)) todo.append(lambda: getFunc(2)(1)) todo.append(lambda: getFunc(3)(1)) for task in todo: print task() --- the program outputs: 4 4 4 2 3 4 in Python 2.6. is that excpected? -- http://mail.python.org/mailman/listinfo/python-list
Re: Tkinter and asyncronous socket
[EMAIL PROTECTED] wrote: > Hi all, I'm new to python and I've been spending the last week on GUI > that refresh its content based on data periodically coming from a > remote socket. > I succeded in doing it (thanks newsgroups and online manual!) using > the Tkinter.after method to implement a busy wait on the socket (which > I had previously set to non blocking) > I should be happy with it, but on windows (application must be multi- > platform) the busy wait leads to a 100% CPU usage. I'm trying to > implement it the other way round: a "socket process" that updates a > label (or a queue object) in the GUI. I can't figure out how to do > this. Anyone can post hints? With some details, maybe? > Processes are probably a bit heavyweight for this purpose: they create difficulties in communication (unless you use the new multiprocessing library in 2.6). One approach would be to run the socket code in blocking mode in a separate thread started by the (main program) GUI thread at program startup, and communicating results back via a Queue.Queue or similar to the GUI thread. That thread wakes itself up once every (say) 500 mS to check for updates from the socket side. You should see your CPU utilization go down then. The threading.thread library is actually much easier to use than you would think, though it's possible to get things wrong by assuming data sharing will work in ways it actually doesn't. But if you have the main thread pass a Queue to the networking thread, that should be a reliable means of communication. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Multiple equates
In article <[EMAIL PROTECTED]>, Lawrence D'Oliveiro <[EMAIL PROTECTED]> wrote: >Cameron Laird wrote: > >> I've been trying to decide if there's any sober reason to advocate >> the one-liner >> >> map(lambda i: a.__setitem__(i, False), [x1, x2, x3, ..., x1024]) > >Are lambdas like the Dark Side of Python? > >:) Enough so, apparently, that I'm reluctant even to touch that question. -- http://mail.python.org/mailman/listinfo/python-list
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Re: Is the behavior expected?
Alphones: > it is a little deferent from other script language. See also here: http://en.wikipedia.org/wiki/Dynamic_scope#Dynamic_scoping Python doesn't have such automatic closures, probably for performance reasons and/or maybe to keep its C implementation simpler (maybe other people here can give you an explanation of this, I too am curious). Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
Cong Ma <[EMAIL PROTECTED]> wrote:
> Thanks for your reply. I checked my Python 2.5 install on Linux and there's
> the
> O_DIRECTORY flag. However this is not mentioned anywhere in the Library
> Reference.
>
> There's another question regarding to this flag though: I checked the manual
> of
> the Linux system call open(2), in which there's a paragraph on this flag:
>
> O_DIRECTORY
>If pathname is not a directory, cause the open to fail.
> This
>flag is Linux-specific, and was added in kernel version
> 2.1.126,
>to avoid denial-of-service problems if opendir(3) is called on
> a
>FIFO or tape device, but should not be used outside of
> the
>implementation of opendir(3).
That says avoid to me!
> Note the "should not be used outside of the implementation of opendir(3)"
> part.
> Does that mean using Python's os.open() with the O_DIRECTORY flag is a Bad
> Thing?
IMHO yes.
> In C, I think, calling opendir() followed by dirfd() should be the
> correct way of doing this?
Here is how you do exactly that in python using ctypes
from ctypes import CDLL, c_char_p, c_int, Structure, POINTER
from ctypes.util import find_library
class c_dir(Structure):
"""Opaque type for directory entries, corresponds to struct DIR"""
c_dir_p = POINTER(c_dir)
c_lib = CDLL(find_library("c"))
opendir = c_lib.opendir
opendir.argtypes = [c_char_p]
opendir.restype = c_dir_p
dirfd = c_lib.dirfd
dirfd.argtypes = [c_dir_p]
dirfd.restype = c_int
closedir = c_lib.closedir
closedir.argtypes = [c_dir_p]
closedir.restype = c_int
dir_p = opendir(".")
print "dir_p = %r" % dir_p
dir_fd = dirfd(dir_p)
print "dir_fd = %r" % dir_fd
print "closed (rc %r)" % closedir(dir_p)
Which prints on my linux machine
dir_p =
dir_fd = 3
closed (rc 0)
I don't know why os doesn't wrap - opendir, closedir, dirfd, readdir
etc - I guess because except if you are doing something esoteric, then
os.list and os.walk do everything you could possibly want.
--
Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick
--
http://mail.python.org/mailman/listinfo/python-list
Re: Getting in to metaprogramming
"Aaron Brady" <[EMAIL PROTECTED]> wrote: >I don't know a clean, reliable way to structure a metaprogram though. >Mine always turn out messy. Yes. Then another thing - it strikes me that any problem that can be solved by metaprogramming, can be solved by putting similar code into a class and instanciating an instance. Does anybody know if this is true? If it is, it limits the usefulness of metaprogramming to the creation of "stored procedures" for "later execution". - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Xah Lee wrote: In many languages, they don't have namespace and is often a well known sour point for the lang. For example, Scheme has this problem up till R6RS last year. PHP didn't have namespace for the past decade till about this year. Javascript, which i only have working expertise, didn't have namespace as he mentioned in his blog. Elisp doesn't have name space and it is a well known major issue. Namespaces are useful for one reason: they allow you to have conflicts with names in some cases. In Java, there are two Lists: java.awt.List and java.util.List. Since a name must only be unique within a namespace, you can use shorter names without fear of conflict. In languages without these namespaces, you end up with stuff like g_type_init, e_data_server_module_init, mysql_connect, etc., where the prefixes are used to emulate the unique nature of namespaces. Of languages that do have namespace that i have at least working expertise: Mathematica, Perl, Python, Java. Knowing these langs sufficiently well, i do not see anything special about namespace. Most features aren't sufficiently appreciated until one has to do without it. The avoidance of collision that comes with namespaces has shown to be sufficiently useful that I doubt we'll ever see a future major language that doesn't have some sort of namespace feature. > The _essence_ of namespace is that a char is choosen as a separator, and the compiler just use this char to split/connect identifiers. That's just composition of namespace names. It's not what namespaces is about. i cannot fathom what could possibly be difficult of introducing or implementing a namespace mechanism into a language. Namespaces go to the very core of a language, name resolution. Retroactively adding such a feature is extremely difficult because there is a strong chance of accidentally breaking existing code. > I do not understand, why so many languages that lacks so much needed namespace for so long? If it is a social problem, i don't imagine they would last so long. It must be some technical issue? It's technical: it would be difficult to retroactively implement such a feature. -- Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth -- http://mail.python.org/mailman/listinfo/python-list
Apache & mod_python: I don't receive anything with POST method
Hi,
I'm using a simple form to make possible the users of our site upload
files.
The "upload.py" looks like this:
from mod_python import apache, util;
def index(req):
form = util.FieldStorage(req, keep_blank_values=1)
try:
# form is empty here
# return form --> I get "{}"
ufile = form.get('upfile', None)
if not form.has_key('upfile'):
return ":( No 'upfile' key"
# some checks. I never get beyond here
ufile = form['upfile']
if ufile.file:
return ufile.file.name
else:
return ":( It's not a file"
except Exception, e:
return 'Fail: ' + str(e)
I'm getting an empty 'form'. No 'upfile' key at all. I've tried to add
some other text fields but the result is the same: empty. If I use GET
method with text fields, it works properly.
Currently I'm using:
Apache 2.2.9 (initially I used Apache 2.2.3 too)
mod_python 3.3.1 (initially I used mod_python 3.2.10 too)
Python 2.5.2
Thanks
Best regards,
León
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Re: Using dictionary to hold regex patterns?
André a écrit :
(snip)
you don't need to use pattern.items()...
Here is something I use (straight cut-and-paste):
def parse_single_line(self, line):
'''Parses a given line to see if it match a known pattern'''
for name in self.patterns:
result = self.patterns[name].match(line)
FWIW, this is more expansive than iterating over (key, value) tuples
using dict.items(), since you have one extra call to dict.__getitem__
per entry.
if result is not None:
return name, result.groups()
return None, line
where self.patterns is something like
self.patterns={
'pattern1': re.compile(...),
'pattern2': re.compile(...)
}
The one potential problem with the method as I wrote it is that
sometimes a more generic pattern gets matched first whereas a more
specific pattern may be desired.
As usual when order matters, the solution is to use a list of (name,
whatever) tuples instead of a dict. You can still build a dict from this
list when needed (the dict initializer accepts a list of (name, object)
as argument).
--
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Re: Reg Expression - Get position of >
On Wed, Nov 26, 2008 at 1:48 AM, M_H <[EMAIL PROTECTED]> wrote: > On Nov 25, 11:06 pm, r <[EMAIL PROTECTED]> wrote: >> On Nov 25, 4:33 pm, Jorgen Grahn <[EMAIL PROTECTED]> wrote: >> >> >> >> > On Tue, 25 Nov 2008 12:41:53 -0800 (PST), r <[EMAIL PROTECTED]> wrote: >> > > On Nov 25, 10:36 am, M_H <[EMAIL PROTECTED]> wrote: >> > >> Hey, >> >> > >> I need the position of the last char > >> >> > >> Let's say I have a string >> > >> mystr =
Re: Is the behavior expected?
On 11月26日, 下午8时48分, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote: > Alphones wrote: > > Hi all, > > > def getFunc(x): > > return lambda y : x + y > > > if __name__ == '__main__': > > todo = [] > > proc = getFunc(1) > > todo.append(lambda: proc(1)) > > proc = getFunc(2) > > todo.append(lambda: proc(1)) > > proc = getFunc(3) > > todo.append(lambda: proc(1)) > > > todo.append(lambda: getFunc(1)(1)) > > todo.append(lambda: getFunc(2)(1)) > > todo.append(lambda: getFunc(3)(1)) > > > for task in todo: > > print task() > > > --- > > the program outputs: > > 4 > > 4 > > 4 > > 2 > > 3 > > 4 > > in Python 2.6. > > is that excpected? > > Yes. Creating a lambda will close over the current *names* in the scope, > *not* their respective values. For that, you need to create a new scope - > e.g. by bindig the value to a argument of the lambda: > > lambdas = [] > for i in xrange(10): > lambda i=i : i ** 2 > > for l in lambdas: > l() > > Diez thanks :D now I know what's wrong with my program. it is a little deferent from other script language. -- http://mail.python.org/mailman/listinfo/python-list
Re: Official definition of call-by-value (Re: Finding the instance reference...)
On 2008-11-20, greg <[EMAIL PROTECTED]> wrote: > Antoon Pardon wrote: > >> You are changing your argument. In a follow up you >> made the point that call by value should be as it >> was intended by the writers of the algol 60 report. > > No, I was countering the argument that "call by value" > is short for "call by copying the value". I was pointing > out that the inventors of the term didn't use any such > words. That doesn't counter that that was intended. > Arguing that their words were intended to imply copying, > as part of the essence of the idea, is making an even > bigger assumption about their intentions, IMO. In their document assignment was a copying. IMO the bigger assumption is to assume that these people wanted to define "call by value" for languages which would have different assignment semantics than their own. > Rather it seems to me that the essence of the idea they > had in mind is that call-by-value is equivalent to > assignment. In their particular context. > Furthermore, I don't seem to be alone in coming to that > conclusion -- the designers of other dynamic languages > appear to be using the same logic when they describe > their parameter passing as call-by-value. So what. Some designers do and some don't and some make a particular effort to do different. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
Re: Security implications of using open() on untrusted strings.
On Tue, 25 Nov 2008 23:37:25 +0100, News123 <[EMAIL PROTECTED]> wrote:
> Jorgen Grahn wrote:
>> Compare with a language (does Perl allow this?) where if the string
>> is "rm -rf /|", open will run "rm -rf /" and start reading its output.
>> *That* interface would have been
> Good example. (for perl):
I should actually have removed that paragraph from my posting.
I was about to write "*That* interface would have been dangerous!" but
then I thought "Hm, isn't the user supposed to be in control of that
string, and isn't it his fault if he enters '-rm -rf |', just as if
he entered the name of his most valuable file?"
I don't know ...
> The problem doesn't exist in python
> open("rm -rf / |") would try to open a file with exactly that name and
> it would fail if it doesn't exist.
>
> In perl the perl script author has the choice to be safe (three argument
> open) or to allow stupid or nice things with a two argument open.
...
> Sometimes I miss the 'dangerous variation' in python and I explicitely
> add code in python that the filename '-' will be treated as stdin for
> files to be read and as stdout for files to be written to
That's something I frequently do, too. And I see no harm in it, if I
document it and people expect it (for those who don't know, reserving
'-' for this is a Unix tradition).
/Jorgen
--
// Jorgen Grahn R'lyeh wgah'nagl fhtagn!
--
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Re: How to get a directory file descriptor?
Nick Craig-Wood wrote:
> Here is how you do exactly that in python using ctypes
>
> from ctypes import CDLL, c_char_p, c_int, Structure, POINTER
> from ctypes.util import find_library
>
> class c_dir(Structure):
> """Opaque type for directory entries, corresponds to struct DIR"""
> c_dir_p = POINTER(c_dir)
>
> c_lib = CDLL(find_library("c"))
> opendir = c_lib.opendir
> opendir.argtypes = [c_char_p]
> opendir.restype = c_dir_p
> dirfd = c_lib.dirfd
> dirfd.argtypes = [c_dir_p]
> dirfd.restype = c_int
> closedir = c_lib.closedir
> closedir.argtypes = [c_dir_p]
> closedir.restype = c_int
>
> dir_p = opendir(".")
> print "dir_p = %r" % dir_p
> dir_fd = dirfd(dir_p)
> print "dir_fd = %r" % dir_fd
> print "closed (rc %r)" % closedir(dir_p)
>
> Which prints on my linux machine
>
> dir_p =
> dir_fd = 3
> closed (rc 0)
>
> I don't know why os doesn't wrap - opendir, closedir, dirfd, readdir
> etc - I guess because except if you are doing something esoteric, then
> os.list and os.walk do everything you could possibly want.
>
Thank you so much Nick. I'll take a look into the ctypes module.
I guess the reason of Python library not including those wrappers has something
to do with standard compliance. The fchdir(2) manual says "comforming to
POSIX.1-2001" but the opendir(3) manual says "fdopendir() is specified in
POSIX.1-2008."
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Re: How to get a directory file descriptor?
On Nov 26, 11:07 pm, Steve Holden <[EMAIL PROTECTED]> wrote: > alex23 wrote: > > I'm pretty certain it was present under Windows XP as well. > > Since these two are the exact same version I presume O_DIRECTORY is not > meaningful on Windows. Anyway, when I try to use O_RDONLY on Vista I get > "Permission denied": Sorry, my bad. I got the exact same "Permission denied" response when I first tried this under XP, so I shelled to a linux box and tested there...then promptly forgot all about it. In my defence, it was pretty late at night when I did so :) In fact, I can't even find a reference to O_DIRECTORY in the manual at all... -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting in to metaprogramming
On Nov 26, 11:55 pm, "Hendrik van Rooyen" <[EMAIL PROTECTED]> wrote: > Then another thing - it strikes me that any problem that can be solved > by metaprogramming, can be solved by putting similar code into a class > and instanciating an instance. > > Does anybody know if this is true? > > If it is, it limits the usefulness of metaprogramming to the creation > of "stored procedures" for "later execution". > > - Hendrik Many times (probably most times) you can avoid code generation and use classes or higher order functions instead. Actually I don't like code generation techniques in Python and other languages. I would make an exception for Lisp-like languages, however, since there you a pretty powerful macro mechanism that in some cases can be better than using higher order functions, especially if performance is important. I say something more in the latest episode of my "Adventures of a Pythonista in Schemeland" which some of you may find interesting: http://www.artima.com/weblogs/viewpost.jsp?thread=240836 M. Simionato -- http://mail.python.org/mailman/listinfo/python-list
Re: confused about classes and tkinter object design
marc wyburn a écrit : Hi, I've created my first Tkinter GUI class which consists of some buttons that trigger functions. I have also created a tkFileDialog.askdirectory control to local a root folder for log files. I have several file paths that depend on the value of tkFileDialog.askdirectory should I create an object that inherits this value or can I point functions at the GUI class? I am creating the tkinter GUI instance using; if __name__ == "__main__": GUI = AuditorGUI() Note that at this point, the AuditorGUI class is not yet defined, so you should get a NameError. GUI.mainloop() > class AuditorGUI(Frame): I assume you have all necessary imports in your real code... def __init__(self): Frame.__init__(self) self.pack(expand = YES, fill = BOTH) ## Create GUI objects self.currentdir = StringVar() self.currentdir.set(os.getcwd()) self.logdir = Button(self, text="Choose Data directory",command=self.choose_dir) self.logdir.grid(row=1,column=0,sticky='nsew',pady=20,padx=20) self.labeldirpath = Label(self, textvariable=self.currentdir) def choose_dir(self): dirname = tkFileDialog.askdirectory (parent=self,initialdir=self.currentdir.get(),title='Please select a directory') if len(dirname ) > 0: self.currentdir.set(dirname) I think I have created an instance of the AuditorGUI class called GUI so should be able to access the path using GUI.currentdir but this doesn't work. "does not work" is (almost) the less possible usefull description of a problem. What happens exactly ? Do you have a traceback ? If so, please post the full traceback and error message. Else, please explain what result you get. And if possible, post minimal *working* code reproducing the problem. I'm still struggling with classes so not sure whether my problem is tkinter related or not. Minus the couple problems above (ie: trying to instanciate a non-yet-existing class, and lack of necessary imports), it seems correct - at least wrt/ class definition and instanciation. -- http://mail.python.org/mailman/listinfo/python-list
Python C/API simple debugging
Hi all,
I am new to Python C API and finding it difficult to debug C
extensions. So, basically I want to see the value of an integer value
during the C API. Here is the code:
#define LAST_MIX_VAL 0xDEADBEEF
static PyObject *
chash(PyObject *self, PyObject *args)
{
unsigned int key,result; //treat key like an usinged int.
unsigned char a,b,c,d;
key = result = 0;
if (!PyArg_ParseTuple(args, "i", &key))
return NULL;
printf("Key:%i\n",Py_BuildValue("i", key));
.
.
So, I just want to see the contents of local variable key. If I call
printf(..) without Py_BuildValue(), the interpreter shuts down, because
(I am assuming) printf is allocating some value in heap that is not in
the interpreter's heap itself which is causing the corruption.
This way it works, but this time I cannot see correct key content.
So, questions are:
- What I am doing wrong here?
- What is the preffered approach for these kind simple-debugging
issue? I searched C/API ref but cannot see any help on that?
Thanks,
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Re: Python surpasses Perl in popularity?
Roy Smith wrote: > In article <[EMAIL PROTECTED]>, > Jorgen Grahn <[EMAIL PROTECTED]> wrote: > >> Hard to take a popularity index seriously when Logo is at #19 and >> Bourne shell at #32 ... and then they suggest that their readers can >> use it "to make a strategic decision about what programming language >> should be adopted when starting to build a new software system". > > When you've seen some of the shell scripts I've seen, it's not hard to > imagine that logo might be a better choice of programming language. :) In fact all that's really happened is that Perl has slid down the ranks, at least temporarily. Python has been around the 6/7 mark for a while now. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Reg Expression - Get position of >
On Nov 25, 11:06 pm, r <[EMAIL PROTECTED]> wrote: > On Nov 25, 4:33 pm, Jorgen Grahn <[EMAIL PROTECTED]> wrote: > > > > > On Tue, 25 Nov 2008 12:41:53 -0800 (PST), r <[EMAIL PROTECTED]> wrote: > > > On Nov 25, 10:36 am, M_H <[EMAIL PROTECTED]> wrote: > > >> Hey, > > > >> I need the position of the last char > > > > >> Let's say I have a string > > >> mystr =
Re: what's so difficult about namespace?
On Nov 26, 5:45 am, Joshua Cranmer <[EMAIL PROTECTED]> wrote: > > i cannot fathom what could possibly be difficult of > > introducing or implementing a namespace mechanism into a language. > > Namespaces go to the very core of a language, name resolution. > Retroactively adding such a feature is extremely difficult because there > is a strong chance of accidentally breaking existing code. could you give some technical detail on this? i don't know compiler so am probably being foolish here... but i suppose ultimately name resolution and storage at heart is something like a hashtable... namely, put ‹identifier 1› table put ‹identifier 2› table and lookup is just retrieve ‹identifier› table and now suppose we introduced namespace, so i imagine the compiler simply just concat namespace component befor put, and split before retrieve? Xah ∑ http://xahlee.org/ ☄ -- http://mail.python.org/mailman/listinfo/python-list
Re: zope vs openACS
Bruno Desthuilliers <[EMAIL PROTECTED]> wrote: > Stefan Scholl a écrit : >> [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: >>> On Nov 19, 1:50 am, gavino <[EMAIL PROTECTED]> wrote: what is nicer about each? >>> Yes. >> >> And No. >> > Or maybe ? This isn't Haskell. -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
alex23 wrote:
> On Nov 26, 3:26 pm, greg <[EMAIL PROTECTED]> wrote:
>> os.O_DIRECTORY must be fairly new -- it doesn't exist
>> in my 2.5 installation. But os.O_RDONLY seems to work
>> just as well for this purpose.
>
> Which OS are you using?
>
> Python 2.5.2 (r252:60911, Jul 31 2008, 17:28:52)
> [GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
import os
hasattr(os, 'O_DIRECTORY')
> True
>
> I'm pretty certain it was present under Windows XP as well.
>
OK, here's a little mystery. This is Vista (spit):
Microsoft Windows [Version 6.0.6001]
Copyright (c) 2006 Microsoft Corporation. All rights reserved.
C:\Users\sholden>python
Python 2.5.2 (r252:60911, Feb 21 2008, 13:11:45) [MSC v.1310 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> f = os.open(".", os.O_DIRECTORY)
Traceback (most recent call last):
File "", line 1, in
AttributeError: 'module' object has no attribute 'O_DIRECTORY'
>>> hasattr(os, 'O_DIRECTORY')
False
>>>
Since these two are the exact same version I presume O_DIRECTORY is not
meaningful on Windows. Anyway, when I try to use O_RDONLY on Vista I get
"Permission denied":
>>> f = os.open(os.path.abspath("Documents"), os.O_RDONLY)
Traceback (most recent call last):
File "", line 1, in
OSError: [Errno 13] Permission denied: 'C:\\Users\\sholden\\Documents'
regards
Steve
--
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Holden Web LLC http://www.holdenweb.com/
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Re: Python/C API: using from a shared library
On 2008-11-25, Robie Basak <[EMAIL PROTECTED]> wrote: > If I use dlopen() to open a shared library that I've written, and that > shared library tries to use the Python/C API, then it fails. I've > reduced the problem to the test case below. The error is: > > ImportError: /usr/lib/python2.5/lib-dynload/time.so: undefined symbol: > PyExc_ValueError I've submitted a bug for this. See http://bugs.python.org/issue4434 for an more detailed explanation and a workaround. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python C/API simple debugging
On Nov 26, 2008, at 6:47 AM, k3xji wrote:
By the way for simple print-debugging, below works right now, I
forgot
to try that
fprintf(stderr,"%d", key);
As a new extension developer myself, I'll pass along the following
handy macro that I swiped from another extension (psycopg I think):
#ifdef DEBUG_ON
#define DPRINTF(fmt, args...) fprintf(stderr, "+++ " fmt, ## args)
#else
#define DPRINTF(fmt, args...)
#endif
You can use it in code like so:
DPRINTF("key == %d\n", key);
And then turn all of your debug statements on/off by recompiling with/
without the DEBUG_ON flag.
HTH
Philip
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Re: Python surpasses Perl in popularity?
Steve Holden wrote: In fact all that's really happened is that Perl has slid down the ranks, at least temporarily. Python has been around the 6/7 mark for a while now. Also.. can someone attempt to explain the funny correlation in popularity over time between, for instance, Python and Delphi? :-) -- http://mail.python.org/mailman/listinfo/python-list
How to use Py_DEBUG ?
Hello, Does somebody know how to debug this kind of bug ? (see following traceback) I suppose that the bug is in my program (executable with python embedded) and not in python... but how to locate it ? I tried to compile all C sources calling Python.h with -DPy_DEBUG and to link my code against config_d/libpython2.5.a, but I get no more information. Is it the right way ? Can gc module get interesting information ? #0 0x093179a9 in visit_decref (op=0x302e3020, data=0x0) at ../Modules/ gcmodule.c:270 #1 0x0928c4c1 in dict_traverse (op=0xa315214, visit=0x9317976 , arg=0x0) at ../Objects/dictobject.c:1892 #2 0x09317a74 in subtract_refs (containers=0x96802c8) at ../Modules/ gcmodule.c:295 #3 0x09318746 in collect (generation=2) at ../Modules/gcmodule.c:790 #4 0x09319245 in PyGC_Collect () at ../Modules/gcmodule.c:1265 #5 0x0930857a in Py_Finalize () at ../Python/pythonrun.c:389 #6 0x0930b5ef in Py_Exit (sts=0) at ../Python/pythonrun.c:1618 #7 0x09309caf in handle_system_exit () at ../Python/pythonrun.c:1054 #8 0x09309ccd in PyErr_PrintEx (set_sys_last_vars=1) at ../Python/ pythonrun.c:1064 #9 0x093099df in PyErr_Print () at ../Python/pythonrun.c:978 #10 0x0930944e in PyRun_SimpleFileExFlags (fp=0x9ce6900, filename=0xbf840644 "Python/Execution/E_SUPERV.py", closeit=1, flags=0xbf83fbb0) at ../Python/pythonrun.c:883 #11 0x09308b7c in PyRun_AnyFileExFlags (fp=0x9ce6900, filename=0xbf840644 "Python/Execution/E_SUPERV.py", closeit=1, flags=0xbf83fbb0) at ../Python/pythonrun.c:698 #12 0x09317648 in Py_Main (argc=23, argv=0xbf83fcc4) at ../Modules/ main.c:523 #13 0x0809eaa9 in main (argc=23, argv=0xbf83fcc4) Thanks, MC -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting in to metaprogramming
On Thu, 27 Nov 2008 00:55:33 +0200, Hendrik van Rooyen wrote: > "Aaron Brady" <[EMAIL PROTECTED]> wrote: > > >>I don't know a clean, reliable way to structure a metaprogram though. >>Mine always turn out messy. > > Yes. > > Then another thing - it strikes me that any problem that can be solved > by metaprogramming, can be solved by putting similar code into a class > and instanciating an instance. > > Does anybody know if this is true? Well, I don't know about "any problem". And it's not so much about whether metaprograms can solve problems that can't be solved by anything else, as whether metaprograms can solve problems more effectively than other techniques. If you include factory functions, class factories, the builder design pattern, metaclasses, etc. as "metaprogramming", then I use it all the time, and find it an excellent technique to use. But if you mean using a Python program to generate Python source code, then I can't think of any time I used it. Which doesn't mean that others don't find it helpful, only that I haven't yet. Thinking further back, when I was young and programming in Apple's Hypercard 4GL, I used to frequently use Hypercard scripts to generate new Hypercard scripts. That was to work around the limitations of the scripting language. I don't think metaprogramming in the limited sense (programs to output source code) is a bad idea, but I do think that there are probably better alternatives in a language like Python. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Is the behavior expected?
On 11月26日, 下午9时28分, [EMAIL PROTECTED] wrote: > Alphones: > > > it is a little deferent from other script language. > > See also here:http://en.wikipedia.org/wiki/Dynamic_scope#Dynamic_scoping > > Python doesn't have such automatic closures, probably for performance > reasons and/or maybe to keep its C implementation simpler (maybe other > people here can give you an explanation of this, I too am curious). > > Bye, > bearophile i encountered this problem when i'm writing a program for packaging files. the program generates tasks according to description file. and tasks are deferent from each other, and should be excuted at the last of program. i have experience on Lua and have learned about scheme and haskell, so i wrote the wrong code in python. now my solution is, using class taskCreator to create tasks and put them into tasklist. class taskCreator: def __init__(self, proc, input, output): self.proc = proc self.input = input self.output = output def call(self): return self.proc.call(self.input, self.output) 'proc' is generated by procCreators, it's specified. it looks more complex than lambda one. is there any other simple way to implement it? and does the taskCreator mean 'create a new scope'? Suggestions will be appreciated. Thanks. PS: i'm a newbie in Python (started from today) -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
On Nov 26, 8:56 pm, Cong Ma <[EMAIL PROTECTED]> wrote: > Thanks for your reply. I checked my Python 2.5 install on Linux and there's > the > O_DIRECTORY flag. However this is not mentioned anywhere in the Library > Reference. Yes, I just noticed that myself. > O_DIRECTORY > If pathname is not a directory, cause the open to fail. This > flag is Linux-specific, and was added in kernel version 2.1.126, Well, that certainly explains it's absence :) > Note the "should not be used outside of the implementation of opendir(3)" > part. > Does that mean using Python's os.open() with the O_DIRECTORY flag is a Bad > Thing? I'm sorry, that's outside of my knowledge. But it seemed to work fine when I tried it. -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Xah Lee wrote: Of languages that do have namespace that i [sic] have at least working expertise: Mathematica, Perl, Python, Java. Knowing these langs sufficiently well, i [sic] do not see anything special about namespace. The _essence_ of namespace is that a char is choosen as a separator, and the compiler just use this char to split/connect identifiers. That is hardly the essence of namespaces, just a notational convenience to help humans relate to namespaces. The essence of namespaces is that they are distinct. It's also not an accurate statement. XML namespaces, for example, use many characters as separators, not just one, but that's not the essence. The essence is that all the characters matter, not just the putative separators. Although i [sic] have close to zero knowledge about compiler or parser, but from a math point of view and my own 18 years of programing experience, i [sic] cannot fathom what could possibly be difficult of introducing or implementing a namespace mechanism into a language. I do not understand, why so many languages that lacks so much needed Point not proven. If they were really needed in every language, every language would have them. namespace for so long? If it is a social problem, i [sic] don't imagine they would last so long. It must be some technical issue? Yeah, like technically they aren't needed everywhere. Could any compiler expert give some explanation? Compilers are not relevant. XML has namespaces, and compilers certainly aren't the issue there. -- Lew -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting in to metaprogramming
On 25 Nov., 11:08, Rafe <[EMAIL PROTECTED]> wrote: > Hi, > > In the name of self-education can anyone share some pointers, links, > modules, etc that I might use to begin learning how to do some > "metaprogramming". That is, using code to write code (right?) > > Cheers, > > - Rafe http://www.letmegooglethatforyou.com/?q=python+metaprogramming -- http://mail.python.org/mailman/listinfo/python-list
Re: [lambda]Is the behavior expected?
Alphones wrote: > Hi all, > > > def getFunc(x): > return lambda y : x + y > > if __name__ == '__main__': > todo = [] > proc = getFunc(1) > todo.append(lambda: proc(1)) > proc = getFunc(2) > todo.append(lambda: proc(1)) > proc = getFunc(3) > todo.append(lambda: proc(1)) > > todo.append(lambda: getFunc(1)(1)) > todo.append(lambda: getFunc(2)(1)) > todo.append(lambda: getFunc(3)(1)) > > for task in todo: > print task() > > --- > the program outputs: > 4 > 4 > 4 > 2 > 3 > 4 > in Python 2.6. > is that excpected? Yes. Creating a lambda will close over the current *names* in the scope, *not* their respective values. For that, you need to create a new scope - e.g. by bindig the value to a argument of the lambda: lambdas = [] for i in xrange(10): lambda i=i : i ** 2 for l in lambdas: l() Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Pyhon (with wxPython) on Windows' cygwin: can it be done fully ?
Barak, Ron wrote: > Hi Pythonistas, > > I read diaz's comments with interest, but - in my current configuration, I'm > unable to use pdb. > > I'm developing on cygwin and use wxPython. > Consequently, I cannot use native cygwin Python, but my Python is actually > the Windows XP Python (i.e., /cygdrive/c/Python25/python.exe). > This means that pdb (and, for that matter any Python shell (like IDLE)) gets > stuck upon invocation. > > I was wandering: is anybody able to use native Python on cygwin, or > alternately, to use Windows Python under cygwin in IDLE/pdb ? > That's a pretty crazy combination, which is more or less guaranteed to cause problems. If you are using the standard Windows Python under cygwin you will find it gives you issues with filenames, for example. You won't be able to access them using the Cygwin names, so why not just run the standard Windows Python under the Windows command line? You can, of course, continue to use Cygwin for editing and command-line Python. But you seem to be asking for trouble unnecessarily by running Windows Python under Cygwin. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Python surpasses Perl in popularity?
In article <[EMAIL PROTECTED]>, Marco Mariani <[EMAIL PROTECTED]> wrote: > Steve Holden wrote: > > > In fact all that's really happened is that Perl has slid down the ranks, > > at least temporarily. Python has been around the 6/7 mark for a while now. > > Also.. can someone attempt to explain the funny correlation in > popularity over time between, for instance, Python and Delphi? :-) It's explained in http://en.wikipedia.org/wiki/Delphi. -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Xah Lee wrote: > On Nov 26, 5:45 am, Joshua Cranmer <[EMAIL PROTECTED]> wrote: >>> i cannot fathom what could possibly be difficult of >>> introducing or implementing a namespace mechanism into a language. >> Namespaces go to the very core of a language, name resolution. >> Retroactively adding such a feature is extremely difficult because there >> is a strong chance of accidentally breaking existing code. > > could you give some technical detail on this? > > i don't know compiler so am probably being foolish here... but i > suppose ultimately name resolution and storage at heart is something > like a hashtable... namely, > > put ‹identifier 1› table > put ‹identifier 2› table > > and lookup is just > > retrieve ‹identifier› table > > and now suppose we introduced namespace, so i imagine the compiler > simply just concat namespace component befor put, and split before > retrieve? > And therein lies the danger of imagination. Typically the namespace components are looked up one by one, so for this.that.theother first "this" will be looked up and (hopefully) yield an object with a namespace, which will then be searched for "that", yielding another object with a namespace in which "theother" can be looked up. That's certainly how it works in Python: >>> import os >>> dir(os) [... , 'path', ...] >>> dir(os.path) [... , 'walk'] >>> os.path >>> os.path.walk >>> Using a single global namespace table might work, but only for some horrendously convoluted values of "work". To delete os.path you would have to delete not only the key "os.path" but also all keys beginning with "os,path." -- it's the kind of solution a PHP programmer might have dreamed up. And before anyone bothers to point it out, yes, I know PHO now (finally) has namespaces. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Is the behavior expected?
Alphones wrote: > On 11月26日, 下午9时28分, [EMAIL PROTECTED] wrote: >> Alphones: >> >> > it is a little deferent from other script language. >> >> See also here:http://en.wikipedia.org/wiki/Dynamic_scope#Dynamic_scoping >> >> Python doesn't have such automatic closures, probably for performance >> reasons and/or maybe to keep its C implementation simpler (maybe other >> people here can give you an explanation of this, I too am curious). >> >> Bye, >> bearophile > > i encountered this problem when i'm writing a program for packaging > files. > the program generates tasks according to description file. > and tasks are deferent from each other, and should be excuted at the > last of program. > > i have experience on Lua and have learned about scheme and haskell, so > i wrote the wrong code in python. > > now my solution is, using class taskCreator to create tasks and put > them into tasklist. > class taskCreator: > def __init__(self, proc, input, output): > self.proc = proc > self.input = input > self.output = output > def call(self): > return self.proc.call(self.input, self.output) > 'proc' is generated by procCreators, it's specified. > > it looks more complex than lambda one. > > is there any other simple way to implement it? > and does the taskCreator mean 'create a new scope'? Not exactly, but there is a saying: "Closures are a poor man's objects. And objects are a poor man's closures." What you did creating a class and instantiating was to capture the parameters you needed at a time, and using them within call at another time. A similar thing happens when you create a lambda with arguments assigned, as I showed you - as then as part of the closure of the lambda there are the names in it's parameter list, assigned to the values the right hand sides had at the time being. Depending on what you want to do, both approaches - classes or closures - are valid. The more complex a problem gets, the more explicit & powerful a class becomes, where it might be a bit of an overhead for really simple problems. One thing for example classes allow - which is interesting for you - is that it is easy to look into them, for debugging/tracing. You can take a taskCreator (BTW, read PEP 8 about naming conventions in python) and see what is in there, e.g. logging it before executing the task or some such. OTOH, a lambda (or function) is an opaque thing you can't ask such things, making life a bit harder sometimes. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Enumerating k-segmentations of a sequence
On Nov 26, 12:15 am, [EMAIL PROTECTED] wrote: > bullockbefriending bard napisa³(a): > > > > > I'm not sure if my terminology is precise enough, but what I want to > > do is: > > > Given an ordered sequence of n items, enumerate all its possible k- > > segmentations. > > > This is *not* the same as enumerating the k set partitions of the n > > items because I am only interested in those set partitions which > > preserve the order of the items. i.e. if the input sequence is (1 2 3 > > 4 5), then ((1 4) (2 3) (5)) is unacceptable, whereas ((1 2) (3) (4 > > 5)) is acceptable. Hence use of term 'segmentations'. > > > e.g., for input sequence (1 2 3 4 5) and k = 3, I need a function > > which enumerates the following 3-segmentations: > > > ((1 2 3) (4) (5)) > > ((1 2) (3 4) (5)) > > ((1 2) (3) (4 5)) > > ((1) (2 3 4) (5)) > > ((1) (2 3) (4 5)) > > ((1) (2) (3 4 5)) > > > The reason I want to do this is to use it in some simple one- > > dimensional clustering, i.e. each set item (won't be just integers as > > above) will have a value of interest, and i'll select the particular > > set partition which minimises Sigma SSD (sum of squared differences > > from mean) of these values. > > > It seems overkill to generate the full list of set partitions > > [including e.g. ((1 4) (2) (3 5))] because I intend to begin by > > sorting the input sequence such that element 1 < element 2 < ... < > > element n. > > > Structural Recursion not being my strong point, any ideas on how to go > > about this would be much appreciated! > > I'm not sure if I correctly understood the semantics of what you need. > Anyway it looks like a nice exercise in nested generators: > > def segmentations(sequence, k): > assert 1 <= k <= len(sequence) > if k == 1: > yield [sequence] > else: > for headlen in xrange(1, len(sequence) - k + 2): > head, tail = sequence[:headlen], sequence[headlen:] > for tail_seg in segmentations(tail, k - 1): > yield [head] + tail_seg > > for segmentation in segmentations((1, 2, 3, 4, 5), 3): > print segmentation > > Regards, > Marek Exactly what I needed. Thank you all for examples and also for explaining how to think about problems of this nature! -- http://mail.python.org/mailman/listinfo/python-list
Re: How to get a directory file descriptor?
Steve Holden wrote:
import os
hasattr(os, 'O_DIRECTORY')
True
I'm pretty certain it was present under Windows XP as well.
f = os.open(".", os.O_DIRECTORY)
Traceback (most recent call last):
File "", line 1, in
AttributeError: 'module' object has no attribute 'O_DIRECTORY'
The 3.0 manual lists 4 groups of flags: unix and windows, unix only,
windows only, gnu only (check system-specific manual). O_DIRECTORY is
in the gnu group.
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Re: Python surpasses Perl in popularity?
On Nov 25, 2:47 pm, Jorgen Grahn <[EMAIL PROTECTED]> wrote: > On Mon, 24 Nov 2008 20:25:51 -0500, [EMAIL PROTECTED] <[EMAIL PROTECTED]> > wrote: > > QuotingXahLee<[EMAIL PROTECTED]>: > > >> herald: Python surpasses Perl in popularity! > > >> According to > >> ?TIOBE Programming Community Index for November 2008? at > >>http://www.tiobe.com/content/paperinfo/tpci/index.html > > >> it seems that Python has surpassed Perl in popularity this month! > > Interesting topic ! > > Hard to take a popularity index seriously when Logo is at #19 and > Bourne shell at #32 ... and then they suggest that their readers can > use it "to make a strategic decision about what programming language > should be adopted when starting to build a new software system". your remark is a bit overzealous. After all, we all know that site is websearh based. Although it not some kinda scientific report, but it does give some good indication of language popularity, however you define that. it is conceivable that logo is somewhat used more than bourne shell. first of all, Logo is a lisp dialect. (it's one of the rare lisp sans the parens.) The most famous logo book is the triology titled something like Computer Science Logo Style, by Brian Harvey, who teaches at UC Berkeley and now and then still post to “comp.lang.scheme”. (who, like some many veteran Scheme Lisp dignitaries, cries out against the utter fuckup Scheme 6 (aka R6RS)) Bourne Shell, is pretty much replaced by Bash since several years ago. For example, as far as i know, linuxes today don't have Bourne Shell anymore. “sh” is just a alias to bash with some compatibility parameter. That immediately wipe out a huge sector of unixes that lives on Bourne Shell. This is a good thing. In about 2000 i called for this. The fucking asshole Sun Microsystems insists on installing at least 3 versions of shell utilities in several directories... (and the BSD unixes insist on their inferior stupid versions of shell tools) To be sure, Logo is very much a academic lang, mostly for teaching and for younsters. Much of its code is about drawing graphics. Some other major use of Logo is in robotics, much associated with the Lego robotics toys. While Bourne Shell, as far as i can venture a guess, is still the primary startup scripts in various unixes. It is hard to put down exactly which is “popular”. We have to first define what we mean by popular, of course. Is it number of programers/ users? Popularity in the sense of awareness? Number of software using them out there? etc. However, as mentioned before, all things considered, it is conceivable that Logo is more popular than sh. For one thing, for any use of shell script other than the machine startup scripts, people don't use bourne shell anymore. They use bash, maybe tcsh, and probably vast majority of unix/server shell oriented installation scripts are done in Perl or python today. For those interested in languages, see: • Proliferation of Computing Languages http://xahlee.org/UnixResource_dir/writ/new_langs.html It would be fruitful to actually set aside some 3 hours in some weekend, to read thru these and the Wikipedia articles linked. You'll get a survey of today's languages, what they are, what they do, their nature, their field, and where the landscape of languages might be tomorrow. plain text version follows. --- Back to Computing and Its People. Proliferation of Computing Languages Xah Lee, 2008-07, 2008-11 There is a proliferation of computer languages today like never before. In this page, i list some of them. In the following, i try to list some of the langs that are created after 2000, or become very active after 2000. Functional langs: Erlang↗. Functional, concurrent. Mostly used in a telecomunication industry for corcurrency and continuous up-time features. Haskell↗ Oldish, classic functional lang. Mercury↗. Logic, functional. Q↗. Functional lang, based on term rewriting. To be replaced by Pure↗. Oz↗. Concurrent. Multiparadigm. ML Family: OCaml↗ Alice↗. Concurrent, ML derivative. Saarland University, Germany. F#↗. Microsoft's functional lang. Lisp family or similar: Mathematica↗. Computer algebra system background. Used mostly for math and research. NewLisp↗. Lisp scripting style. Arc↗. Paul Graham squeezing juice out of his celebrity status. Qi↗. Common Lisp added with modern functional lang features. Clojure↗. A new lisp dialect on Java platform. Scheme↗, notably PLT Scheme↗. Used mostly for teaching. (Dead. Dylan↗. Apple's re-invention of lisp for industrial programers, active in the 1990s.) Computer Algebra and Proof systems: Coq↗. For formal proofs. For much more, see Category:Computer algebra systems↗ and Automated theorem proving↗. Perl Family or derivative: PHP↗. Perl derivative for server side web apps. One of the top 10 used langs post 2000. Ruby↗. Perl with rectified syntax and semantics. Perl6↗. Next gen of perl. Sleep↗. A scripting lang, perl syntax. On Java platfor
Re: what's so difficult about namespace?
Xah Lee wrote : i cannot fathom what could possibly be difficult of introducing or implementing a namespace mechanism into a language. I do not understand, why so many languages that lacks so much needed namespace for so long? If it is a social problem, i don't imagine they would last so long. It must be some technical issue? Simply put: - it was not in the original language specification - some hundreds of millions of distributed browsers interpret Javascript without namespaces - to introduce namespaces into the language would require every browser to be replaced (at least if the user comes across a site which uses it) The IT community has enough trouble getting a few ISPs to upgrade their DNS software. How are you going to get millions of general users to upgrade? Web stats show that people are still using IE 5... -- Wojtek :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Is the behavior expected?
Alphones wrote:
> On 11月26日, 下午9时28分, [EMAIL PROTECTED] wrote:
>> Alphones:
>>
>> > it is a little deferent from other script language.
>>
>> See also here:http://en.wikipedia.org/wiki/Dynamic_scope#Dynamic_scoping
>>
>> Python doesn't have such automatic closures, probably for performance
>> reasons and/or maybe to keep its C implementation simpler (maybe other
>> people here can give you an explanation of this, I too am curious).
>>
>> Bye,
>> bearophile
>
> i encountered this problem when i'm writing a program for packaging
> files.
> the program generates tasks according to description file.
> and tasks are deferent from each other, and should be excuted at the
> last of program.
>
> i have experience on Lua and have learned about scheme and haskell, so
> i wrote the wrong code in python.
>
> now my solution is, using class taskCreator to create tasks and put
> them into tasklist.
> class taskCreator:
> def __init__(self, proc, input, output):
> self.proc = proc
> self.input = input
> self.output = output
> def call(self):
> return self.proc.call(self.input, self.output)
> 'proc' is generated by procCreators, it's specified.
>
> it looks more complex than lambda one.
>
> is there any other simple way to implement it?
Yes, you can have closures in Python (you already had one, the getFunc()
function in your initial post).
Random remarks:
You don't need an explicit call() method, you can make instances callable:
>>> class A:
... def __init__(self, name):
... self.name = name
... def __call__(self):
... print "calling", self.name
...
>>> a = A("foo")
>>> a()
calling foo
If your object has just this one method you can instead use a closure:
>>> def make_a(name):
... def call():
... print "calling", name
... return call
...
>>> a = make_a("bar")
>>> a()
calling bar
This can be simplified further with some help from the library:
>>> from functools import partial
>>> def call(name):
... print "calling", name
...
>>> a = partial(call, "baz")
>>> a()
calling baz
Here is a complete example:
import sys
from functools import partial
def lower(input, output):
output.writelines(line.lower() for line in input)
def prefix(input, output):
for index_line in enumerate(input):
output.write("%d: %s" % index_line)
tasks = [partial(lower, open("tmp.py"), sys.stdout),
partial(prefix, open("tmp.py"), sys.stdout)]
for t in tasks:
t()
Peter
--
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Re: Python surpasses Perl in popularity?
Xah Lee wrote: > On Nov 25, 2:47 pm, Jorgen Grahn <[EMAIL PROTECTED]> wrote: >> On Mon, 24 Nov 2008 20:25:51 -0500, [EMAIL PROTECTED] <[EMAIL PROTECTED]> >> wrote: >>> QuotingXahLee<[EMAIL PROTECTED]>: herald: Python surpasses Perl in popularity! According to ?TIOBE Programming Community Index for November 2008? at http://www.tiobe.com/content/paperinfo/tpci/index.html it seems that Python has surpassed Perl in popularity this month! >>> Interesting topic ! >> Hard to take a popularity index seriously when Logo is at #19 and >> Bourne shell at #32 ... and then they suggest that their readers can >> use it "to make a strategic decision about what programming language >> should be adopted when starting to build a new software system". > > your remark is a bit overzealous. After all, we all know that site is > websearh based. Although it not some kinda scientific report, but it > does give some good indication of language popularity, however you > define that. > [... rant omitted ...] I wondered how long you would be able to resist making your vituperative remarks. Please stop this rubbish. regards Steve -- Steve Holden+1 571 484 6266 +1 800 494 3119 Holden Web LLC http://www.holdenweb.com/ -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Xah Lee wrote: > > i cannot fathom what could possibly be difficult of > > introducing or implementing a namespace mechanism into a language. I > > do not understand, why so many languages that lacks so much needed > > namespace for so long? If it is a social problem, i don't imagine they > > would last so long. It must be some technical issue? On Nov 26, 8:06 am, Wojtek <[EMAIL PROTECTED]> wrote: > Simply put: > - it was not in the original language specification > - some hundreds of millions of distributed browsers interpret > Javascript without namespaces > - to introduce namespaces into the language would require every browser > to be replaced (at least if the user comes across a site which uses it) > > The IT community has enough trouble getting a few ISPs to upgrade their > DNS software. How are you going to get millions of general users to > upgrade? > > Web stats show that people are still using IE 5... alright, that's speaks for Javascript. But how's that apply to, say, Scheme lisp, Emacs lisp, PHP? In the case of Scheme, i can see that the problem of delay in introducing namespace is due to the nature of community wanting some consensus on the most elegant approach. For emacs lisp, is it prolonged lack of namespace due to lack of developer resource? in anycase, the reasons above are social ones. Namely, issues like backward compatibility, agreement on design, lack of developers. I'd be very interested if any compiler writer can give technical perspective on whether introducing namespace to a existing lang is a problem. Xah ∑ http://xahlee.org/ ☄ -- http://mail.python.org/mailman/listinfo/python-list
Re: Is the behavior expected?
On Nov 26, 2:28 pm, [EMAIL PROTECTED] wrote: > Alphones: > > > it is a little deferent from other script language. > > See also here:http://en.wikipedia.org/wiki/Dynamic_scope#Dynamic_scoping > > Python doesn't have such automatic closures, probably for performance > reasons and/or maybe to keep its C implementation simpler (maybe other > people here can give you an explanation of this, I too am curious). Python has closures which are just fine. The issue here is the for loop. In Python (as in Common Lisp) the for loop works by *mutating* a single loop index. The closures will get the latest value of the loop index. In Haskell or Scheme the natural way to define a for loop is by introducing a new index variable at each iteration: there is no mutation. Each closure get its own index, with the right value. It is a design choice: Guido and the Common Lisp implementors are happy with mutating the loop index. I myself prefer the functional way. Michele Simionato -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Xah Lee wrote: >> The IT community has enough trouble getting a few ISPs to upgrade their >> DNS software. How are you going to get millions of general users to >> upgrade? > > alright, that's speaks for Javascript. > > But how's that apply to, say, Scheme lisp, Emacs lisp, PHP? Think before you write. It's exactly the same thing. How would you get all Emacs users in the world to upgrade? Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
On Nov 26, 11:42 am, Stefan Behnel <[EMAIL PROTECTED]> wrote: > Xah Lee wrote: > >> The IT community has enough trouble getting a few ISPs to upgrade their > >> DNS software. How are you going to get millions of general users to > >> upgrade? > > > alright, that's speaks for Javascript. > > > But how's that apply to, say, Scheme lisp, Emacs lisp, PHP? > > Think before you write. It's exactly the same thing. How would you get all > Emacs users in the world to upgrade? The same way you would get all Python users to upgrade to 3.0 ? It's not like Joe User runs emacs to edit his grocery store list. George -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
On Nov 26, 8:42 am, Stefan Behnel <[EMAIL PROTECTED]> wrote: > XahLeewrote: > >> The IT community has enough trouble getting a few ISPs to upgrade their > >> DNS software. How are you going to get millions of general users to > >> upgrade? > > > alright, that's speaks for Javascript. > > > But how's that apply to, say, Scheme lisp, Emacs lisp, PHP? > > Think before you write. It's exactly the same thing. How would you get all > Emacs users in the world to upgrade? Hi Stefan, try not to be a moron. In the case of javascript, it involves web servers and clients (web browsers). In the case of Scheme Lisp or Emacs Lisp, there's no such server/client issue. There is still the compatibilty issue, but not the same scenario as javascript. As compatibility issue, that doesn't just apply to namespaces but to any othe function or change in the language. And as you know, language changes all the time, in big or small dosages. Small changes happens almost every release. Major changes happens every few years (e.g. Java versions thru the year, Perl4 to perl5, each iteration of Scheme's RnRS) So, in general, backward compatibility does not fully answer the question of the no namespace problem. Even if it does, the detail or reason is not given in the above and is not something obvious at least to me. Xah ∑ http://xahlee.org/ ☄ -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Xah Lee wrote: > i cannot fathom what could possibly be difficult of > introducing or implementing a namespace mechanism into a language. Joshua Cranmer wrote: >> Namespaces go to the very core of a language, name resolution. >> Retroactively adding such a feature is extremely difficult because there >> is a strong chance of accidentally breaking existing code. Xah Lee wrote: > > could you give some technical detail on this? > > > i don't know compiler so am probably being foolish here... but i > > suppose ultimately name resolution and storage at heart is something > > like a hashtable... namely, > > > put ‹identifier 1› table > > put ‹identifier 2› table > > > and lookup is just > > > retrieve ‹identifier› table > > > and now suppose we introduced namespace, so i imagine the compiler > > simply just concat namespace component befor put, and split before > > retrieve? Steve Holden wrote: > And therein lies the danger of imagination. > Typically the namespace components are looked up one by one, so for > >this.that.theother > > first "this" will be looked up and (hopefully) yield an object with a > namespace, which will then be searched for "that", yielding another > object with a namespace in which "theother" can be looked up. That's > certainly how it works in Python: yes, but Steve, what is your point? The question is, what is the technical difficulty, if any, of introducing namespace into a existing language. You pointed out that identifier lookup at least from the perspective of language user is somewhat like a tree walking processing. However, that does not answer the main question. Xah ∑ http://xahlee.org/ ☄ -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
"Steve Holden" <[EMAIL PROTECTED]> wrote: > And before anyone bothers to point it out, yes, I know PHO now (finally) > has namespaces. I cannot resist oulling the oiss... Its not the first time... :-) - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting in to metaprogramming
"Steven D'Aprano" wrote: > > Well, I don't know about "any problem". And it's not so much about > whether metaprograms can solve problems that can't be solved by anything > else, as whether metaprograms can solve problems more effectively than > other techniques. > > If you include factory functions, class factories, the builder design > pattern, metaclasses, etc. as "metaprogramming", then I use it all the > time, and find it an excellent technique to use. > > But if you mean using a Python program to generate Python source code, > then I can't think of any time I used it. Which doesn't mean that others > don't find it helpful, only that I haven't yet. I am using the term in the restricted sense of Python writing Python source. Given that, can anybody think of an example that you could not do with a class? (excepting the "stored procedure" aspect) Or can I claim a new a new meta - rule - I would call it van Rooyen's folly... > > Thinking further back, when I was young and programming in Apple's > Hypercard 4GL, I used to frequently use Hypercard scripts to generate new > Hypercard scripts. That was to work around the limitations of the > scripting language. What sort of stuff did you do, and would having had simple OO available have rendered it unnecessary? > > I don't think metaprogramming in the limited sense (programs to output > source code) is a bad idea, but I do think that there are probably better > alternatives in a language like Python. > > True. No argument here - I was just wondering if the relationship holds. - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
import in a class
Hi everybody,
Here is a file "test_import_scope.py":
##
class a():
import re
def __init__( self ):
if re.search( "to", "toto" ):
self.se = "ok!"
def print_se( self ):
print self.se
a().print_se()
##
When python executes this file, we obtain an error:
$ python test_import_scope.py
[...]
NameError: global name 're' is not defined
Why?
When the re module is imported in the __init__ function or out of the class
(at the top of the file), it works obviously perfectly.
Thanks in advance,
Julien
--
python -c "print ''.join([chr(154 - ord(c)) for c in '*9(9&(18%.9&1+,\'Z
(55l4('])"
"When a distinguished but elderly scientist states that something is
possible, he is almost certainly right. When he states that something is
impossible, he is very probably wrong." (first law of AC Clarke)
--
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Re: import in a class
On Wed, Nov 26, 2008 at 9:30 AM, TP <[EMAIL PROTECTED]> wrote:
> Hi everybody,
>
> Here is a file "test_import_scope.py":
> ##
> class a():
> import re
> def __init__( self ):
> if re.search( "to", "toto" ):
> self.se = "ok!"
> def print_se( self ):
> print self.se
> a().print_se()
> ##
>
> When python executes this file, we obtain an error:
>
> $ python test_import_scope.py
> [...]
> NameError: global name 're' is not defined
>
> Why?
Because Python doesn't look in class-scope when doing name resolution.
It checks the local [function] namespace, then any nested [function]
scopes (not applicable in this case), then the module/global
namespace, and finally the builtins namespace. The class' namespace
never comes into the equation.
Consider this simpler example (remember that `import` assigns a module
to its name in the importing scope):
>>> class Foo(object):
... A=1
... def foo(self): print A
...
>>> Foo().foo()
Traceback (most recent call last):
File "", line 1, in
File "", line 3, in foo
NameError: global name 'A' is not defined
So in foo(), `A` can be accessed by Foo.A or self.A, but not just plain `A`.
I agree it's not entirely intuitive, but remember that Python != Java.
Cheers,
Chris
--
Follow the path of the Iguana...
http://rebertia.com
>
> When the re module is imported in the __init__ function or out of the class
> (at the top of the file), it works obviously perfectly.
>
> Thanks in advance,
>
> Julien
>
> --
> python -c "print ''.join([chr(154 - ord(c)) for c in '*9(9&(18%.9&1+,\'Z
> (55l4('])"
>
> "When a distinguished but elderly scientist states that something is
> possible, he is almost certainly right. When he states that something is
> impossible, he is very probably wrong." (first law of AC Clarke)
> --
> http://mail.python.org/mailman/listinfo/python-list
>
--
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Is it possible (and wise) to extend the None-type ?
hello, I've the idea that I always have a lot of useless code in my programs, like the next example. def _On_Menu_File_Open ( self, event = None ): if event : event.Skip () instead of def _On_Menu_File_Open ( self, event = None ): event.Skip () So I would like to extend the None-type (if that's possible), with a dummy Skip() method. Is it wise to do ? If not what are the disadvantages ? thanks, Stef Mientki -- http://mail.python.org/mailman/listinfo/python-list
best IDE
Which one is the best IDE for python -- http://mail.python.org/mailman/listinfo/python-list
Re: best IDE
On Wed, Nov 26, 2008 at 9:59 AM, asit <[EMAIL PROTECTED]> wrote: > Which one is the best IDE for python This was recently discussed. To avoid needlessly rehashing said discussion, see the thread at http://groups.google.com/group/comp.lang.python/browse_thread/thread/7fd136aef1c63e47/fbaff90068f0fe02 Cheers, Chris -- Follow the path of the Iguana... http://rebertia.com > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
Re: best IDE
On Nov 26, 11:09 pm, "Chris Rebert" <[EMAIL PROTECTED]> wrote: > On Wed, Nov 26, 2008 at 9:59 AM, asit <[EMAIL PROTECTED]> wrote: > > Which one is the best IDE for python > > This was recently discussed. To avoid needlessly rehashing said > discussion, see the thread > athttp://groups.google.com/group/comp.lang.python/browse_thread/thread/... > > Cheers, > Chris > -- > Follow the path of the Iguana...http://rebertia.com > > > -- > >http://mail.python.org/mailman/listinfo/python-list Thanx -- http://mail.python.org/mailman/listinfo/python-list
Re: Is it possible (and wise) to extend the None-type ?
On Wed, Nov 26, 2008 at 9:55 AM, Stef Mientki <[EMAIL PROTECTED]> wrote: > hello, > > I've the idea that I always have a lot of useless code in my programs, > like the next example. > > def _On_Menu_File_Open ( self, event = None ): > if event : >event.Skip () > > instead of > > def _On_Menu_File_Open ( self, event = None ): > event.Skip () > > So I would like to extend the None-type (if that's possible), It's not. You can't graft new methods onto NoneType (a.k.a. type(None)), and you can't subclass NoneType either. You might be interested in the recipe for a "Null" type: http://code.activestate.com/recipes/68205/ Cheers, Chris -- Follow the path of the Iguana... http://rebertia.com > with a dummy Skip() method. > > Is it wise to do ? > If not what are the disadvantages ? > > thanks, > Stef Mientki > > > > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
Re: Getting in to metaprogramming
On 27 Nov., 05:41, "Hendrik van Rooyen" <[EMAIL PROTECTED]> wrote: > Given that, can anybody think of an example that you could not do with > a class? (excepting the "stored procedure" aspect) I just noticed that corepy 1.0 [1] has been released. Corepy is an embedded DSL for synthesizing machine code from chaining Python commands. This means it provides objects and exploits control structures used to create machine code that can finally be executed interactively. Let's say you have an ordinary Python function that computes a CRC 32. Now you could attempt to translate the function into other Python code that expresses a corepy routine. You could create a decorator that works as follows 1) reads the source of the decorated function 2) transforms the source into corepy source and compiles it or 3) if 2) fails it just returns the passed code object. Kay [1] http://www.corepy.org/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Reg Expression - Get position of >
On Wed, 26 Nov 2008 01:48:59 -0800 (PST), M_H <[EMAIL PROTECTED]> wrote:
> On Nov 25, 11:06 pm, r <[EMAIL PROTECTED]> wrote:
>> On Nov 25, 4:33 pm, Jorgen Grahn <[EMAIL PROTECTED]> wrote:
...
>> > Depends on if you have an irrational fear of REs or not ... I agree
>> > that REs are overused for things which are better done with split, but
>> > in this case I think an RE would be clearer.
>>
>> > >>> re.sub('.*>', '', 'dkjk>djdd')
...
> I want to have the end-position of the mimetype tag (position as
> mystr.find('>') returns, so I can use the number for a loop)
> However, I can't use just the '>' because the character > could also
> be in the string of mimetype (I know, actually not in mimetype, but
> let's assume it).
> So that is why the filter shall be bulletproof and check for '">' -
> with possible spaces between both characters.
OK. I am too tired to think it through, but if you need to handle
nesting brackets or escaped brackets (e.g. ignore brackets inside
double-quoted strings) then an RE is not the best solution.
/Jorgen
--
// Jorgen Grahn R'lyeh wgah'nagl fhtagn!
--
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Re: Is it possible (and wise) to extend the None-type ?
On Nov 27, 4:55 am, Stef Mientki <[EMAIL PROTECTED]> wrote: > hello, > > I've the idea that I always have a lot of useless code in my programs, > like the next example. > > def _On_Menu_File_Open ( self, event = None ): > if event : > event.Skip () > > instead of > > def _On_Menu_File_Open ( self, event = None ): > event.Skip () > > So I would like to extend the None-type (if that's possible), > with a dummy Skip() method. > > Is it wise to do ? No. > If not what are the disadvantages ? Assume that as well as your Event class, you also have a Foo class with a dothis method and a Bar class with a dothat1 and a dothat2 method: you would need to extend the None-type (if that's possible) to have dummy skip, dothis, dothat1 and dothat2 methods. Each time you invent a new class, you need to consider adding one or more new dummy methods to your extended None-type. Alternative (if you *really* want to save the explicit test) is to attach the behaviour modification to the *relevant* class: class NonEvent(Event): def do_nothing(self): pass skip = jump = hop = waltz = saunter = do_nothing def __len__(self): return 0 NON_EVENT = NonEvent() del NonEvent # later: def amethod(self, event=NON_EVENT): if event: # still works thanks to __len__ above event.skip() # now can avoid test, if desired event.skip() HTH ... BTW, ever heard of PEP 8? Cheers, John -- http://mail.python.org/mailman/listinfo/python-list
Re: best IDE
On Nov 26, 11:59 am, asit <[EMAIL PROTECTED]> wrote: > Which one is the best IDE for python You'll probably also want to take a look at the Python wiki: http://wiki.python.org/moin/PythonEditors Mike -- http://mail.python.org/mailman/listinfo/python-list
newbie question
Hello, I just started to use Python. I wrote the following code and expected 'main' would be called. def main(): print "hello" main But I was wrong. I have to use 'main()' to invoke main. The python interpreter does not give any warnings for the above code. Is there any way/tool to easily detect this kind of errors ? Thanks ! -- http://mail.python.org/mailman/listinfo/python-list
Python equivalent of Common Lisp Macros?
I'm using the feedparser library to extract data from rss feed items.
After I wrote this function, which returns a list of item titles, I
noticed that most item attributes would be retrieved the same way,
i.e., the function would look exactly the same, except for the single
data.append line inside the for loop.
In CL, I could simply write a macro, then replace the data.append line
depending on which attribute I wanted.
Is there anything similar in Python?
Here's the function:
def item_titles (feed_url):
"""Return a list of the item titles found in this feed url"""
data = []
feed = feedparser.parse(feed_url)
if feed:
if len(feed.version) > 0:
for e in feed.entries:
data.append(e.title.encode('utf-8'))
return data
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Re: newbie question
On Wed, 2008-11-26 at 11:11 -0800, Nan wrote: > Hello, >I just started to use Python. I wrote the following code and > expected 'main' would be called. > > def main(): > print "hello" > > main > > But I was wrong. I have to use 'main()' to invoke main. The python > interpreter does not give any warnings for the above code. Is there > any way/tool to easily detect this kind of errors ? > Syntactically your code is correct, so the interpreter just goes about its business. You can usually use tools such as pylint or pychecker to find find such issues. For example, pylint reports (among other things): W: 4: Statement seems to have no effect -- http://mail.python.org/mailman/listinfo/python-list
Re: newbie question
On Wed, Nov 26, 2008 at 11:11 AM, Nan <[EMAIL PROTECTED]> wrote: > Hello, > I just started to use Python. I wrote the following code and > expected 'main' would be called. > > def main(): > print "hello" > > main > > But I was wrong. I have to use 'main()' to invoke main. The python > interpreter does not give any warnings for the above code. Is there > any way/tool to easily detect this kind of errors ? Python has first-class functions, so you can pass a function to another function (so the line `main` has a meaning, just not a useful one). Also, Python doesn't do compile-time typechecking, so it has no way of knowing that `main` is a function and not a plain variable until runtime. Thus, the parentheses are required for a function call even when there are no arguments. Cheers, Chris -- Follow the path of the Iguana... http://rebertia.com > > Thanks ! > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
Re: Instance attributes vs method arguments
In article <[EMAIL PROTECTED]>, M.-A. Lemburg <[EMAIL PROTECTED]> wrote: > >It is always good practice to provide default values for instance >variables in the class definition, both to enhance readability and to >allow adding documentation regarding the variables, e.g. Actually, my company uses an occasional pattern of detecting whether an attribute has ever been set with hasattr(). I am not particularly fond of that mechanism because it has been the occasional source of subtle bugs, but I also see the utility. -- Aahz ([EMAIL PROTECTED]) <*> http://www.pythoncraft.com/ "It is easier to optimize correct code than to correct optimized code." --Bill Harlan -- http://mail.python.org/mailman/listinfo/python-list
Re: Python equivalent of Common Lisp Macros?
On Wed, Nov 26, 2008 at 11:13 AM, dpapathanasiou
<[EMAIL PROTECTED]> wrote:
> I'm using the feedparser library to extract data from rss feed items.
>
> After I wrote this function, which returns a list of item titles, I
> noticed that most item attributes would be retrieved the same way,
> i.e., the function would look exactly the same, except for the single
> data.append line inside the for loop.
>
> In CL, I could simply write a macro, then replace the data.append line
> depending on which attribute I wanted.
>
> Is there anything similar in Python?
Yes, use higher-order functions. See below.
>
> Here's the function:
>
> def item_titles (feed_url):
Replace previous line with:
def item_titles(feed_url, attr_getter):
>"""Return a list of the item titles found in this feed url"""
>data = []
>feed = feedparser.parse(feed_url)
>if feed:
>if len(feed.version) > 0:
>for e in feed.entries:
>data.append(e.title.encode('utf-8'))
Replace previous line with:
data.append(attr_getter(e))
>return data
Example usage:
def title_getter(entry):
return entry.title.encode('utf-8')
titles = item_titles("some feed url here", title_getter)
As I'm not familiar with feedparser, you might want to move where the
.encode() takes place, but you get the idea.
Cheers,
Chris
--
Follow the path of the Iguana...
http://rebertia.com
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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Re: Python equivalent of Common Lisp Macros?
dpapathanasiou schrieb:
I'm using the feedparser library to extract data from rss feed items.
After I wrote this function, which returns a list of item titles, I
noticed that most item attributes would be retrieved the same way,
i.e., the function would look exactly the same, except for the single
data.append line inside the for loop.
In CL, I could simply write a macro, then replace the data.append line
depending on which attribute I wanted.
Is there anything similar in Python?
Here's the function:
def item_titles (feed_url):
"""Return a list of the item titles found in this feed url"""
data = []
feed = feedparser.parse(feed_url)
if feed:
if len(feed.version) > 0:
for e in feed.entries:
data.append(e.title.encode('utf-8'))
return data
No, there are no macros. Yet it has - amongst other options, such as
callbacks - decorators, that would allow you to write your code like this:
def items (feed_url):
feed = feedparser.parse(feed_url)
if feed:
if len(feed.version) > 0:
for e in feed.entries:
yield e
titles = []
other_things = []
for item in items(url):
titles.append(item.title.encode('utf-8'))
other_things.append(item.other_thing)
Diez
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Re: Getting in to metaprogramming
Hendrik van Rooyen wrote: I am using the term in the restricted sense of Python writing Python source. Given that, can anybody think of an example that you could not do with a class? (excepting the "stored procedure" aspect) I am not sure I understand your question. def iterize(recursive_function_text): return equivalent_iterative_function_text where input and output are both Python code. If one were to implement this by compiling the input to AST form and then walking the tree, the AST node classes would be involved, but I would scarely say the translation was done by the classes, as opposed to functions which might or might not be attacked to a class as methods. tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: Python equivalent of Common Lisp Macros?
dpapathanasiou <[EMAIL PROTECTED]> writes:
> I'm using the feedparser library to extract data from rss feed items.
>
> After I wrote this function, which returns a list of item titles, I
> noticed that most item attributes would be retrieved the same way,
> i.e., the function would look exactly the same, except for the single
> data.append line inside the for loop.
>
> In CL, I could simply write a macro, then replace the data.append line
> depending on which attribute I wanted.
>
> Is there anything similar in Python?
>
> Here's the function:
>
> def item_titles (feed_url):
> """Return a list of the item titles found in this feed url"""
> data = []
> feed = feedparser.parse(feed_url)
> if feed:
> if len(feed.version) > 0:
> for e in feed.entries:
> data.append(e.title.encode('utf-8'))
> return data
Something like this?
def item_attrs (feed_url, attr):
"""Return a list of the item titles found in this feed url"""
data = []
feed = feedparser.parse(feed_url)
if feed:
if len(feed.version) > 0:
for e in feed.entries:
data.append(getattr(e, attr).encode('utf-8'))
return data
You're not making it clear how the data.append... line changes so it's
hard to know exactly.
--
Arnaud
--
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Re: Is it possible (and wise) to extend the None-type ?
Stef Mientki wrote: hello, I've the idea that I always have a lot of useless code in my programs, like the next example. def _On_Menu_File_Open ( self, event = None ): if event : event.Skip () instead of def _O So I would like to extend the None-type (if that's possible), with a dummy Skip() method. def Skipper(object): def Skip(): pass skipper = Skipper() def _On_Menu_File_Open ( self, event = skipper ): event.Skip () etc. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python equivalent of Common Lisp Macros?
dpapathanasiou <[EMAIL PROTECTED]> writes:
> I'm using the feedparser library to extract data from rss feed items.
>
> After I wrote this function, which returns a list of item titles, I
> noticed that most item attributes would be retrieved the same way,
> i.e., the function would look exactly the same, except for the single
> data.append line inside the for loop.
>
> In CL, I could simply write a macro, then replace the data.append line
> depending on which attribute I wanted.
>
> Is there anything similar in Python?
>
> Here's the function:
>
> def item_titles (feed_url):
> """Return a list of the item titles found in this feed url"""
> data = []
> feed = feedparser.parse(feed_url)
> if feed:
> if len(feed.version) > 0:
> for e in feed.entries:
> data.append(e.title.encode('utf-8'))
> return data
No macros -- need the whole "code as data" paradigm which doesn't exist
in python.
The pythonic way to create the sort of abstraction you're looking for
would be to use the *attr functions and either a map of attribute
identities or inspect the attributes from the objects.
Some UNTESTED code...
def extract_entry(e, attrs=['title', 'datetime', 'article']):
out = []
for attr in attrs:
assert hasattr(e, attr)
out.append(getattr(e, attr))
return out
Using the inspect module would give an even more generic function, but
with more complex code of course.
Then your code would look more like:
def items(feed_url):
feed = feedparser.feed(feed_url)
if feed and len(feed) > 0:
return [extract_entry(entry) for entry in feed.entries]
Of course, I'm making liberal assumptions about what you're looking for
in your ouput here... but it's just an example, not a full
solution. YMMV. Hope it helps. :)
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Re: what's so difficult about namespace?
On Nov 26, 9:15 am, Xah Lee <[EMAIL PROTECTED]> wrote: > On Nov 26, 5:45 am, Joshua Cranmer <[EMAIL PROTECTED]> wrote: > > > > i cannot fathom what could possibly be difficult of > > > introducing or implementing a namespace mechanism into a language. > > > Namespaces go to the very core of a language, name resolution. > > Retroactively adding such a feature is extremely difficult because there > > is a strong chance of accidentally breaking existing code. > > could you give some technical detail on this? > > i don't know compiler so am probably being foolish here... but i > suppose ultimately name resolution and storage at heart is something > like a hashtable... namely, > > put ‹identifier 1› table > put ‹identifier 2› table > > and lookup is just > > retrieve ‹identifier› table > > and now suppose we introduced namespace, so i imagine the compiler > simply just concat namespace component befor put, and split before > retrieve? > > Xah > ∑http://xahlee.org/ > > ☄ I'm sorry for the earlier post. I read your question too quickly. I've implemented a few research compilers; none in production. You're totally right in the case where the language has general nested lexical scoping. Namespaces just add an "outermost" scope. If you've done a good engineering job, the compiler change is trivial. In fact I added namespaces like this to an assembler that had lexical scoping. It took about an hour including writing a test suite. If you already have a bunch of compilers for a language like pre- namespace C or Javascript or Basic that doesn't allow for lexical scoping, then the addition is likely to be non-trivial because the implementation compiler language is often C and C programmers will tend to declare a single, global symbol table. So adding a separate outer scope involves hunting down all the global references and replacing them with references to the current namespace table. We can tut tut about this being bad design, but there you have it... -- http://mail.python.org/mailman/listinfo/python-list
Python+Pyjamas+V8=ftw
I don't know how much the community knows about this - i haven't been participating much of late - but here's something amazing. Apparently javascript is just as dynamic as python, because someone made a python-to-javascript converter in just 1200 line (pyjamas). Meanwhile google's new javascript engine (v8) blew all the others out the water, raising the bar - and now safari and firefox already have already risen to that bar with their own jit js engines. The exciting thing is that python code converted to javascript runs on v8 10 times faster (http://www.advogato.org/article/985.html). Thus google's strategy in making the JIT compiler represents what Python could (and should) be. Python should either adapt v8, Tamarin (http://en.wikipedia.org/wiki/Tamarin_(JavaScript_engine), or similar to make its own JIT, or take their basic principles (http://www.youtube.com/watch?v=lZnaaUoHPhs) and recreate them for its own JIT from scratch. Until then, we can always install v8/tamarin/tracemonkey/squirrelfish and easily make a front-end that automatically uses pyjamas to convert python script to JS and runs it. Perhaps pyjamas needs some improvement to fully implement Python - the homepage isn't very clear on how exactly the JS implementation mirrors the Python implementation. Also I suppose it doesn't support Python 3.0 and would have to be changed to support that. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python equivalent of Common Lisp Macros?
On Nov 26, 2:30 pm, "Chris Rebert" <[EMAIL PROTECTED]> wrote:
> On Wed, Nov 26, 2008 at 11:13 AM, dpapathanasiou
>
> <[EMAIL PROTECTED]> wrote:
> > I'm using the feedparser library to extract data from rss feed items.
>
> > After I wrote this function, which returns a list of item titles, I
> > noticed that most item attributes would be retrieved the same way,
> > i.e., the function would look exactly the same, except for the single
> > data.append line inside the for loop.
>
> > In CL, I could simply write a macro, then replace the data.append line
> > depending on which attribute I wanted.
>
> > Is there anything similar in Python?
>
> Yes, use higher-order functions. See below.
>
>
>
> > Here's the function:
>
> > def item_titles (feed_url):
>
> Replace previous line with:
> def item_titles(feed_url, attr_getter):>"""Return a list of the item
> titles found in this feed url"""
> >data = []
> >feed = feedparser.parse(feed_url)
> >if feed:
> >if len(feed.version) > 0:
> >for e in feed.entries:
> >data.append(e.title.encode('utf-8'))
>
> Replace previous line with:
> data.append(attr_getter(e))
>
> >return data
>
> Example usage:
>
> def title_getter(entry):
> return entry.title.encode('utf-8')
>
> titles = item_titles("some feed url here", title_getter)
Thanks; this is exactly what I was looking for.
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asp versus cgi
when i use cgi, i never get a 500 error but i can see how it might
take on overhead if many users are hitting the site at once. so to
avoid this, i looked into registering the python engine for ASP
requests.
when i use asp (C:\WINDOWS\system32\inetsrv\asp.dll fileversion
info:"--a-- W32i DLL ENU 5.1.2600.5512 shp369,664 04-14-2008
asp.dll") , i get intermittent results. it either works or generates a
500 error. the error pattern is 200, 500, 200, 500, 200, 500 and so
on.
this is the ASP code when using GET method:
<%@ LANGUAGE = Python%>
<%
import sys
sys.stdout=sys.stdin
usr = Request.QueryString("usr")
Response.Write ("usr")
%>
**
this is the ASP code when using the POST method
<%@ LANGUAGE = Python%>
<%
import sys
sys.stdout=sys.stdin
usr = Request.Form ("usr")
Response.Write (str(usr))
%>
**
POST by the way seems to have a 100 kb limit so why ever use it unless
you need to keep the data out of the URL?)
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hello from colombia
I work in a small software company using php all day, I wish the usage of Python was more common within my company they are starting a new project (insurance stuff) using Java, and I just hate that eventually I'l be debugging someone-else's java code how can I convince them that Python is better, and get them to re- think their strategy? also, kuddos on the language, you serve mankind as few do. fel. -- http://mail.python.org/mailman/listinfo/python-list
asp oddness , why specify ASP twice
for some reason this code works:
*
<%@ LANGUAGE = Python%>
<%
Response.Write ("test")
%>
*
but this code does NOT:
*
<%@ LANGUAGE = Python
Response.Write ("test")
%>
*
the difference between the two is that i remove "%>" from the first
line and removed "<%" from the next line.
it would seem that this should put all the code into one "ASP block"
but for some reason it does not run.
any ideas? thanks
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Re: Is it possible (and wise) to extend the None-type ?
On Nov 26, 11:40 am, Terry Reedy <[EMAIL PROTECTED]> wrote: > Stef Mientki wrote: > > hello, > > > I've the idea that I always have a lot of useless code in my programs, > > like the next example. > > > def _On_Menu_File_Open ( self, event = None ): > > if event : > > event.Skip () > > > instead of > > > def _O > > > So I would like to extend the None-type (if that's possible), > > with a dummy Skip() method. > > def Skipper(object): > def Skip(): pass > skipper = Skipper() > > def _On_Menu_File_Open ( self, event = skipper ): > event.Skip () > > etc. I think this methods works best, but quite frankly, if a method is only two lines long, then you've likely got a code smell and no amount of over-design is going to cover for it. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is it possible (and wise) to extend the None-type ?
Alternative (if you *really* want to save the explicit test) is to attach the behaviour modification to the *relevant* class: class NonEvent(Event): def do_nothing(self): pass skip = jump = hop = waltz = saunter = do_nothing def __len__(self): return 0 NON_EVENT = NonEvent() del NonEvent # later: def amethod(self, event=NON_EVENT): if event: # still works thanks to __len__ above event.skip() # now can avoid test, if desired event.skip() thanks guys, the Null, Dummy, Skipper, Nonevent class works great HTH ... BTW, ever heard of PEP 8? I guess Python is missing some kind of CSS ;-) cheers, Stef -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
On 2008-11-26, Xah Lee <[EMAIL PROTECTED]> wrote:
> comp.lang.lisp,comp.lang.functional,comp.lang.perl.misc,comp.lang.python,comp.lang.java.programmer
>
> 2008-11-25
>
> Recently, Steve Yegge implemented Javascript in Emacs lisp, and
> compared the 2 languages.
>
> http://steve-yegge.blogspot.com/
> http://code.google.com/p/ejacs/
>
> One of his point is about emacs lisp's lack of namespace.
>
> Btw, there's a question i have about namespace that always puzzled me.
>
> In many languages, they don't have namespace and is often a well known
> sour point for the lang. For example, Scheme has this problem up till
> R6RS last year.
Scheme hasn't officially supported breaking a program into multiple files until
R6RS. If the language is defined in terms of one translation unit, it doesn't
make sense to have a namespace feature.
> PHP didn't have namespace for the past decade till
> about this year. Javascript, which i only have working expertise,
> didn't have namespace as he mentioned in his blog.
Javascript programs are scanned at the character level by the browser as part
of loading a page. So there are severe practical limitations on how large
Javascript programs can be.
Namespaces are useful only in very large programs.
> Elisp doesn't have
> name space and it is a well known major issue.
C doesn't have namespaces, and yet you have projects like the Linux kernel
which get by without this.
Given that the Linux kernel can do without namespaces, it's easy to see how
Javascript and Elisp can survive without it.
> Of languages that do have namespace that i have at least working
> expertise: Mathematica, Perl, Python, Java. Knowing these langs
> sufficiently well, i do not see anything special about namespace. The
> _essence_ of namespace is that a char is choosen as a separator, and
> the compiler just use this char to split/connect identifiers.
The essence of a true namespace or package system or whatever is that you can
establish situations in which you use the unqualified names.
You can emulate namespaces by adding prefixes to identifiers, which is
how people get by in C.
In C, you can even get the functionality of short names using the preprocessor.
I have done this before (but only once). In a widely-used public header file, I
prefixed all of the names of struct members (because struct members are not
immune to clashes: they clash with preprocessor symbols!)
struct foo {
int foo_category;
time_t foo_timestamp;
/* ... */
}
Inside the implementation module, I made macros for myself:
#define category foo_category
#define timestamp foo_timestamp
In this way, I didn't have to edit any of the code in order to move the struct
members into the namespace. Expressions like ``pf->category'' continued to work
as before.
> Although i have close to zero knowledge about compiler or parser, but
> from a math point of view and my own 18 years of programing
> experience, i cannot fathom what could possibly be difficult of
> introducing or implementing a namespace mechanism into a language.
The same things that make it difficult to add anything to a language, namely
the stupid way in which languages are designed to get in the way of extension.
What would it take to add namespaces to C, for instance?
If you have any proposal for a new C feature, the ISO C people encourage you to
develop a proof-of-concept, which means: hack it into an existing
implementation to demonstrate that it's feasible.
If you need new syntax, hacking it into an implementation means hacking it into
the parser. Everyone who wants to experiment with your feature needs to get
your compiler patches (for GCC for instance) and rebuild the compiler.
The process is painful enough that it's only worth doing if it solves something
that is perceived as being a critical issue.
> do not understand, why so many languages that lacks so much needed
> namespace for so long? If it is a social problem, i don't imagine they
> would last so long. It must be some technical issue?
I recently read about a very useful theory which explains why technologies
succeed or fail.
See:
http://arcfn.com/2008/07/why-your-favorite-programming-language-is-unpopular.html
The perceived crisis which namespaces solve is not sigificant enough relative
to the pain of adoption. No, wrong, let's restate that. Programmers do use
namespaces even when there is no language feature. It's not about adoption of
namespaces, but adoption of proper support for namespaces. Not using
namespaces is a crisis in a software project, but (at least in the perception
held by many programmers) that crisis is adequately mitigated by using a naming
convention. Proper namespaces only address the small remaining vestiges
of the original crisis.
Thus: the perceived crisis which is solved by properly incorporating namespaces
into a programming language (rather than living with a prefix-based emulation)
is not significant enough relative to the perceived pain of adopting pr
Re: Is it possible (and wise) to extend the None-type ?
Jason Scheirer wrote: On Nov 26, 11:40 am, Terry Reedy <[EMAIL PROTECTED]> wrote: Stef Mientki wrote: hello, I've the idea that I always have a lot of useless code in my programs, like the next example. def _On_Menu_File_Open ( self, event = None ): if event : event.Skip () instead of def _O So I would like to extend the None-type (if that's possible), with a dummy Skip() method. def Skipper(object): def Skip(): pass skipper = Skipper() def _On_Menu_File_Open ( self, event = skipper ): event.Skip () etc. I think this methods works best, but quite frankly, if a method is only two lines long, then you've likely got a code smell and no amount of over-design is going to cover for it. Sorry I should have said that I only showed the relevant (to this issue) part, and this kind of if statements occurs quit a lot. Probably I should not say this here on this list, but to give you the whole truth, I often forget the if-statement ( because it has really nothing to do with the functionality I intend to write), and then my program crashes (unexpected) :-( cheers, Stef -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
Kaz Kylheku wrote:
On 2008-11-26, Xah Lee <[EMAIL PROTECTED]> wrote:
comp.lang.lisp,comp.lang.functional,comp.lang.perl.misc,comp.lang.python,comp.lang.java.programmer
2008-11-25
Recently, Steve Yegge implemented Javascript in Emacs lisp, and
compared the 2 languages.
http://steve-yegge.blogspot.com/
http://code.google.com/p/ejacs/
One of his point is about emacs lisp's lack of namespace.
Btw, there's a question i have about namespace that always puzzled me.
In many languages, they don't have namespace and is often a well known
sour point for the lang. For example, Scheme has this problem up till
R6RS last year.
Scheme hasn't officially supported breaking a program into multiple files until
R6RS. If the language is defined in terms of one translation unit, it doesn't
make sense to have a namespace feature.
PHP didn't have namespace for the past decade till
about this year. Javascript, which i only have working expertise,
didn't have namespace as he mentioned in his blog.
Javascript programs are scanned at the character level by the browser as part
of loading a page. So there are severe practical limitations on how large
Javascript programs can be.
Namespaces are useful only in very large programs.
Elisp doesn't have
name space and it is a well known major issue.
C doesn't have namespaces, and yet you have projects like the Linux kernel
which get by without this.
Given that the Linux kernel can do without namespaces, it's easy to see how
Javascript and Elisp can survive without it.
Of languages that do have namespace that i have at least working
expertise: Mathematica, Perl, Python, Java. Knowing these langs
sufficiently well, i do not see anything special about namespace. The
_essence_ of namespace is that a char is choosen as a separator, and
the compiler just use this char to split/connect identifiers.
The essence of a true namespace or package system or whatever is that you can
establish situations in which you use the unqualified names.
You can emulate namespaces by adding prefixes to identifiers, which is
how people get by in C.
In C, you can even get the functionality of short names using the preprocessor.
I have done this before (but only once). In a widely-used public header file, I
prefixed all of the names of struct members (because struct members are not
immune to clashes: they clash with preprocessor symbols!)
struct foo {
int foo_category;
time_t foo_timestamp;
/* ... */
}
Inside the implementation module, I made macros for myself:
#define category foo_category
#define timestamp foo_timestamp
In this way, I didn't have to edit any of the code in order to move the struct
members into the namespace. Expressions like ``pf->category'' continued to work
as before.
Although i have close to zero knowledge about compiler or parser, but
from a math point of view and my own 18 years of programing
experience, i cannot fathom what could possibly be difficult of
introducing or implementing a namespace mechanism into a language.
The same things that make it difficult to add anything to a language, namely
the stupid way in which languages are designed to get in the way of extension.
What would it take to add namespaces to C, for instance?
If you have any proposal for a new C feature, the ISO C people encourage you to
develop a proof-of-concept, which means: hack it into an existing
implementation to demonstrate that it's feasible.
If you need new syntax, hacking it into an implementation means hacking it into
the parser. Everyone who wants to experiment with your feature needs to get
your compiler patches (for GCC for instance) and rebuild the compiler.
The process is painful enough that it's only worth doing if it solves something
that is perceived as being a critical issue.
do not understand, why so many languages that lacks so much needed
namespace for so long? If it is a social problem, i don't imagine they
would last so long. It must be some technical issue?
I recently read about a very useful theory which explains why technologies
succeed or fail.
See:
http://arcfn.com/2008/07/why-your-favorite-programming-language-is-unpopular.html
[snip]
The correct URL is
http://arcfn.com/2008/07/why-your-favorite-language-is-unpopular.html
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help with class
Hello, I am playing with class. Below is the code snippet: #!/usr/bin/python 2 3 class test_class: 4#import gzip 5def __init__(self,file): 6 self.file = file 7def open_file(self): 8 try: 9 print "file: %s" % self.file 10 self.xml_file = gzip.GzipFile(self.file,'r') 11 except: 12 print "an exception has occured" 13 for line in self.xml_file: 14 print "line: %s" % line 15 self.xml_file.close() 16 17 18 if __name__ == '__main__': 19import gzip 20import sys 21t = test_class( sys.argv[1] ) 22t.open_file() My question are: 1. Why do I need to use "import gzip" on main section to get it the script to work? I would assume you need the import of gzip in the class section. 2. What is the proper way of using module in a class you are creating? -- http://mail.python.org/mailman/listinfo/python-list
Re: Python surpasses Perl in popularity?
Xah Lee <[EMAIL PROTECTED]> writes: > Bourne Shell, is pretty much replaced by Bash since several years ago. > For example, as far as i know, linuxes today don't have Bourne Shell > anymore. “sh” is just a alias to bash with some compatibility > parameter. That used to be the case, but these days 'sh' is as often an alias to a lighter shell program, a free reimplementation of sh that includes a much smaller superset of the original sh functionality than that of bash. For example, on default Ubuntu installations, sh is a symlink to dash, "a lightweight POSIX-compliant shell derived from ash." -- http://mail.python.org/mailman/listinfo/python-list
Re: what's so difficult about namespace?
On Wed, 26 Nov 2008 21:32:24 +, Kaz Kylheku wrote: > See: > http://arcfn.com/2008/07/why-your-favorite-programming-language-is- unpopular.html That was 404 for me, but http://arcfn.com/2008/07/why-your-favorite-language-is-unpopular.html works. Interesting, thanks for mentioning it. Tamas -- http://mail.python.org/mailman/listinfo/python-list
Re: Is it possible (and wise) to extend the None-type ?
On 2008-11-26 18:55, Stef Mientki wrote: > hello, > > I've the idea that I always have a lot of useless code in my programs, > like the next example. > > def _On_Menu_File_Open ( self, event = None ): >if event : > event.Skip () > > instead of > > def _On_Menu_File_Open ( self, event = None ): > event.Skip () > > So I would like to extend the None-type (if that's possible), > with a dummy Skip() method. > > Is it wise to do ? > If not what are the disadvantages ? This doesn't work. None is a Python singleton that cannot be subclassed. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Nov 26 2008) >>> Python/Zope Consulting and Support ...http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ...http://python.egenix.com/ 2008-11-12: Released mxODBC.Connect 0.9.3 http://python.egenix.com/ Try mxODBC.Zope.DA for Windows,Linux,Solaris,MacOSX for free ! eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 -- http://mail.python.org/mailman/listinfo/python-list
Re: Tkinter and asyncronous socket
On 26 Nov, 13:42, Steve Holden <[EMAIL PROTECTED]> wrote: > [EMAIL PROTECTED] wrote: > > Hi all, I'm new to python and I've been spending the last week on GUI > > that refresh its content based on data periodically coming from a > > remote socket. > > I succeded in doing it (thanks newsgroups and online manual!) using > > theTkinter.after method to implement a busy wait on the socket (which > > I had previously set to non blocking) > > I should be happy with it, but on windows (application must be multi- > > platform) the busy wait leads to a 100% CPU usage. I'm trying to > > implement it the other way round: a "socket process" that updates a > > label (or a queue object) in the GUI. I can't figure out how to do > > this. Anyone can post hints? With some details, maybe? > > Processes are probably a bit heavyweight for this purpose: they create > difficulties in communication (unless you use the new multiprocessing > library in 2.6). > > One approach would be to run the socket code in blocking mode in a > separate thread started by the (main program) GUI thread at program > startup, and communicating results back via a Queue.Queue or similar to > the GUI thread. That thread wakes itself up once every (say) 500 mS to > check for updates from the socket side. > > You should see your CPU utilization go down then. The threading.thread > library is actually much easier to use than you would think, though it's > possible to get things wrong by assuming data sharing will work in ways > it actually doesn't. But if you have the main thread pass a Queue to the > networking thread, that should be a reliable means of communication. > > regards > Steve > -- > Steve Holden +1 571 484 6266 +1 800 494 3119 > Holden Web LLC http://www.holdenweb.com/ Thankk you Steve, I have now a GUI and a threaded socket client receiving data on its socket. I pass to it a queue object from the GUI, but when it tries to push a value on the queue, the GUI does not see any value. My last work with OOP is as far in time as the beginning of Java, I'm surely missing something simple but very important. Anyway, the goal to have a responsive GUI and a functional socket has been achieved, thanks again. If you have hints on the queue problem, your help is welcome. Bye Max -- http://mail.python.org/mailman/listinfo/python-list
