Using len()

[ctilly]

I have what I think is a very simple question.  I have a Python script
that I found that I want to tweek a little bit.  All I want to do is
add in a validator to make sure a value has been keyed into the imput
box.

The code currently is...
while yourguess != mynum:

tries = tries + 1
yourguess = input("Your guess? ")

if  (yourguess != mynum):

#blah blah blah

# end of the if statement
# repeat until user gets it right

But I would like to change it to be something like

while yourguess != mynum:

tries = tries + 1
yourguess = input("Your guess? ")

if len(yourguess)==0:
continue

elif (yourguess != mynum):

#blah blah blah

# end of the if statement
# repeat until user gets it right

But this throws the following error and I have no idea why.  Please
enlighten.

My error ==>  len() of unsized object

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Re: Performance impact of using decorators

[Peter Otten]

vinjvinj wrote:

> I'm building an application with cherrypy and have started using
> decorators quite extensively. A lot of my exposed functions look like:
> 
> @expose
> @startTransactrionAndBuildPage
> @partOfTabUi(tabId)
> @convert(arg1=int, arg2=str)
> def do_main_page(self, arg1, arg2):
>some code
> 
> 
> I've become really fond of decorators and use them quite a lot. I've
> also ready that function calls are expensive in python. In the above
> example, does the interpreter call 5 different functions?

A typical function calls a few other functions already, so three extra
function calls (I suppose expose just sets an attribute) shouldn't matter
much. You shouldn't even start rewriting your code unless you have
identified do_main_page() as a performance bottleneck. In a web app,
candidates would be functions that are called hundred or thousand times per
rendered page rather than once. Does do_main_page() render a complete page?
Forget optimizing three function calls away. You will see no effect.

Peter
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ERROR when hitting RETURN on INPUT

[ctilly]

How do you prevent getting the following error when you hit the RETURN
key on an empty INPUT prompt from windows?

If I am at the Interactive Window and I type in: input("blah"), I get
an input dialog.  If I then hit ENTER w/o keying in a value I get the
following error.  WHY

SyntaxError: unexpected EOF while parsing

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Re: Using len()

[Bryan Olson]

[EMAIL PROTECTED] wrote:
[...]
> But I would like to change it to be something like
> 
> while yourguess != mynum:
> 
>   tries = tries + 1
>   yourguess = input("Your guess? ")
> 
>   if len(yourguess)==0:
>   continue
[...]
> But this throws the following error and I have no idea why.  Please
> enlighten.
> 
> My error ==>  len() of unsized object

The innocent sounding function "input()" actually invokes the perilous
"eval()". Read about it at:

http://docs.python.org/lib/built-in-funcs.html

Try "rawinput()" instead.


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Re: Using len()

[ctilly]

That works, thanks.  Can you tell me why the differences exist?

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Re: counting number of (overlapping) occurances

[Fredrik Lundh]

Steven D'Aprano wrote

> You should always quote enough of the previous poster's message to give
> context. Messages sometimes go missing in Usenet, and people won't have
> the foggiest idea what you are talking about.

one would think that given how many Pythoneers we now have working
for google, at least one of them could go fix the horridly broken posting
interface in googlegroups...

:::

for those who use googlegroups and prefer to make a least a little sense
to people read this newsgroup/mailing list using other tools, please click
"show options" and use the "reply" link at the top of the message instead
of the link with the same name at the bottom.





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OT: Sixteen Thousand Oranges

[Gerard Flanagan]

Dennis Lee Bieber wrote:
> On Sat, 11 Mar 2006 13:30:43 +1100, Tim Churches
> <[EMAIL PROTECTED]> declaimed the following in comp.lang.python:
>
> > Would it be possible to rename "Cheese Shop" as "Bright Side of Life"?
> >
>   I think I'd prefer "The Larch"...
>
>   Or just "SPAM" ( Python  Modules ?)
> --

 ...nostalgic flashback to D.R. and Quinch - 'Something Something
Oranges Something',

and Google provides:  http://mindtheoranges.net/

lol. :-)

Gerard

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Re: Cheese Shop -> BSOL?

[Just]

In article <[EMAIL PROTECTED]>,
 Dennis Lee Bieber <[EMAIL PROTECTED]> wrote:

> On Sat, 11 Mar 2006 13:30:43 +1100, Tim Churches
> <[EMAIL PROTECTED]> declaimed the following in comp.lang.python:
> 
> > Would it be possible to rename "Cheese Shop" as "Bright Side of Life"?
> >
>   I think I'd prefer "The Larch"...
> 
>   Or just "SPAM" ( Python  Modules ?)

Standard Python Archive (of) Modules?

Just
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Re: Using len()

[Fredrik Lundh]

Bryan Olson wrote:

> Try "rawinput()" instead.

or, less likely to give a NameError,

raw_input()





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Re: Using len()

[Jonathan Gardner]

Methinks you are confused about the structure of your program.

If we write the program out in plain English in the form of a recipe,
it should look something like this:

1. Get input.
2. Check to see if they guessed right.
3. If not, go back to 1.

This structure hints at an infinite loop. The breakout condition is a
correct guess. You always need a breakout condition, or the loop goes
on forever. (Sometimes you do want an infinite loop. Think about how
you would write a web server.)

(Note on variable names: "your" and "my" are not clear. Usually, first
person ("I", "me", "my") refers to the programmer. The second person
("you", "your") is rarely used. "You" could be the user, the computer,
or another programmer. Just use third person ("it", "he", "they").

So, we write an infinite loop in Python:

while True:

  # Get input
  guess = raw_input()

  # Is the guess right?
  if guess == num:
# Yep. Break out of the loop.
break

  # Otherwise, loop again.

You could put the breaking condition in the "while" line. But since it
appears in the middle of the loop, this is difficult to do. So just put
it in explicitly in the middle and call it a day.

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Re: Using len()

[Steven D'Aprano]

On Sat, 11 Mar 2006 01:05:48 -0800, ctilly wrote:

> That works, thanks.  Can you tell me why the differences exist?

For those who have just joined us, "that" is using raw_input() instead of
input().

I don't know why input() is the equivalent of eval(raw_input(prompt)), but
it is. Presumably Guido thought it was a good idea at the time. I recall
hearing somewhere that Guido is planning to rename raw_input() to input()
some time in Python 3.


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Inconsistency of special class method lookup?

[anne . nospam01]

Folks,

I'm running into the following issue. A staticmethod of a class seems
not to be accepted as a special class method of the class object
itself. For example:

class Foo(object):
def __len__(): return 2
__len__ = staticmethod(__len__)
print len(Foo)
>>>
Traceback (most recent call last):
  File "C:/Dokumente und Einstellungen/All Users/Dokumente/foo.py",
line 4, in ?
print len(Foo)
TypeError: len() of unsized object

However, the following works:

class FooType(type):
def __len__(self): return self.l()
class Foo(object):
__metaclass__ = FooType
def l(): return 3
l = staticmethod(l)
print len(Foo)
>>>
3

Any good reason why the lookup process doesn't find __len__ as
staticmethod of the class?

Regards,
Sebastian (posting using the account of my wife)

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Re: Using len()

[Fredrik Lundh]

Steven D'Aprano wrote:

> I don't know why input() is the equivalent of eval(raw_input(prompt)), but
> it is. Presumably Guido thought it was a good idea at the time.

possibly inspired by ABC's "READ" and "READ RAW" commands:

http://homepages.cwi.nl/~steven/abc/qr.html





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Re: why no block comments in Python?

[Jonathan Gardner]

Warby wrote:
> ...and I forgot to mention that the output of grep and diff is far more
> understandable in the absence of block comments!

Which is why people do this /anyway/. (Kind of makes block comments
pointless, doesn't it?

/* This is a 
 * really
 * really
 * long
 * block comment */

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Can not find a file in CMD model python when everything is OK in IDLE

[Sullivan WxPyQtKinter]

I use python in Windows XP platform. I find that if I write a .py file
in a directory, such as windows desktop, in which a file named
'ticket.txt' is located:

f=open("\ticket.txt")
print f.read()

In IDLE, this py file work all right. But if I launch python
interpretor in the command shell like this:

C:\Documents and Settings\Xiaozhong Zheng>python "C:\Documents and
Settings\Xiao
zhong Zheng\Desktop\t.py"

The interpretor would not find the file.

Traceback (most recent call last):
  File "C:\Documents and Settings\Xiaozhong Zheng\Desktop\t.py", line
1, in ?
f=open("ticket.txt")
IOError: [Errno 2] No such file or directory: 'ticket.txt'

Anyone knows why?


In addition, if I start IIS web service that runs .py file as CGI
program, then this .py file also works.

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Re: MS Access db (mdb): viewing table attributes

[Steve Holden]

BartlebyScrivener wrote:
> Gau,
> 
> This prints the names of the columns in my database.
> 
> # Modification of
> # http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/389535
> # Instructions for customizing are at:
> # http://www.egenix.com/files/python/mxODBC.html
> 
> import mx.ODBC.Windows as odbc
> 
> driv='DRIVER={Microsoft Access Driver (*.mdb)};DBQ=d:/Access
> Databases/Quotations2005'
> 
> conn = odbc.DriverConnect(driv)
> c = conn.cursor()
> 
> # get the column names from Table1
> c.execute ("SELECT * FROM Table1")
> 
> # get column names
> cols= [ i[0] for i in c.description ]
> print '\n\ncols=',cols
> 
Note that there's no requirement that the SELECT actually retrieve any 
data, son the normal technique is to use a query guaranteed to return no 
rows, such as

 SELECT * FROM Table1 WHERE 1=0

See also

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/81189

for an algorithm that will show data fron an arbitrary query in a 
reasonably tidy display.

regards
  Steve
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Re: time series calculation in list comprehension?

[Peter Otten]

Lonnie Princehouse wrote:

> You really want to use the value calculated for the i_th term in the
> (i+1)th term's evaluation.   

It may sometimes be necessary to recalculate the average for every iteration
to avoid error accumulation. Another tradeoff with your optimization is
that it becomes harder to switch the accumulation function from average to
max, say.

> While it's not easy (or pretty) to store state between iterations in a
> list comprehension, this is the perfect use for a generator:
> 
>   def generator_to_list(f):
> return lambda *args,**keywords: list(f(*args,**keywords))
> 
> [EMAIL PROTECTED]
>   def moving_average(sequence, n):
> assert len(sequence) >= n and n > 0
> average = sum(sequence[:n]) / n
> yield average
> for i in xrange(1, len(sequence)-n+1):
>   average += (sequence[i+n-1] - sequence[i-1]) / n
>   yield average

Here are two more that work with arbitrary iterables:

from __future__ import division

from itertools import islice, tee, izip
from collections import deque

def window(items, n):
it = iter(items)
w = deque(islice(it, n-1))
for item in it:
w.append(item)
yield w # for a robust implementation:
# yield tuple(w)
w.popleft()

def moving_average1(items, n):
return (sum(w)/n for w in window(items, n))

def moving_average2(items, n):
first_items, last_items = tee(items)
accu = sum(islice(last_items, n-1))
for first, last in izip(first_items, last_items):
accu += last
yield accu/n
accu -= first

While moving_average1() is even slower than your inefficient variant,
moving_average2() seems to be a tad faster than the efficient one.

Peter

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Can not find a file in CMD model python when everything is OK in IDLE

[Sullivan WxPyQtKinter]

I use python on Windows XP platform. I find that if I write a .py file
in a directory, such as windows desktop, in which a file named
'ticket.txt' is located:

f=open("ticket.txt")
print f.read()


In IDLE, this py file work all right. But if I launch python
interpretor in the command shell like this:


C:\Documents and Settings\Xiaozhong Zheng>python "C:\Documents and
Settings\Xiaozhong Zheng\Desktop\t.py"


The interpretor would not find the file.


Traceback (most recent call last):
  File "C:\Documents and Settings\Xiaozhong Zheng\Desktop\t.py", line
1, in ?
f=open("ticket.txt")
IOError: [Errno 2] No such file or directory: 'ticket.txt'


Anyone knows why?


In addition, if I start IIS web service that runs .py file as CGI
program, then this .py file also works.

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Re: Can not find a file in CMD model python when everything is OK in IDLE

[Fredrik Lundh]

"Sullivan WxPyQtKinter" wrote:

> I use python in Windows XP platform. I find that if I write a .py file
> in a directory, such as windows desktop, in which a file named
> 'ticket.txt' is located:
>
> f=open("\ticket.txt")
> print f.read()

"\t" is a tab character:

>>> print '\ticket.txt'
icket.txt

try opening r"\ticket.txt" or "/ticket.txt" instead.





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Re: Can not find a file in CMD model python when everything is OK in IDLE

[Sullivan WxPyQtKinter]

Sorry, I mistyped the line. In the program it IS:
f=open("ticket.txt"), no '\' included.

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Re: put multiple condition in if statement

[Terry Hancock]

On 10 Mar 2006 21:12:57 -0800
[EMAIL PROTECTED] wrote:
> How can I put multiple condition in if statement?
> I try this, but I can't get that to work.
> 
> if ( (str != " ") && (str != "") ):

if s!=' ' and s!='':

1) logical operators are words
2) don't overload standard type names

this is actually better style:

if s not in (' ', ''):



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Anansi Spaceworks http://www.AnansiSpaceworks.com

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Re: ERROR when hitting RETURN on INPUT

[Steve Holden]

[EMAIL PROTECTED] wrote:
> How do you prevent getting the following error when you hit the RETURN
> key on an empty INPUT prompt from windows?
> 
> If I am at the Interactive Window and I type in: input("blah"), I get
> an input dialog.  If I then hit ENTER w/o keying in a value I get the
> following error.  WHY
> 
> SyntaxError: unexpected EOF while parsing
> 
Because the input() function expects a Python expression that it can 
evaluate to return a result. You probably want raw_input() instead.

regards
  Steve
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Re: Inconsistency of special class method lookup?

[Peter Otten]

[EMAIL PROTECTED] wrote:

> class Foo(object):
> def __len__(): return 2
> __len__ = staticmethod(__len__)
> print len(Foo)
> >>>
> Traceback (most recent call last):
>   File "C:/Dokumente und Einstellungen/All Users/Dokumente/foo.py",
> line 4, in ?
> print len(Foo)
> TypeError: len() of unsized object
> 
> However, the following works:
> 
> class FooType(type):
> def __len__(self): return self.l()
> class Foo(object):
> __metaclass__ = FooType
> def l(): return 3
> l = staticmethod(l)
> print len(Foo)
> >>>
> 3
> 
> Any good reason why the lookup process doesn't find __len__ as
> staticmethod of the class?

Special methods of newstyle objects are always looked up in the class, and
the class of a class is its metaclass. Therefore 

len(Foo()) invokes type(Foo()).__len__ which is the same as Foo.__len__

and

len(Foo) invokes type(Foo).__len__ which (in your example) is the same as
FooType.__len__.


Peter
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Re: Can not find a file in CMD model python when everything is OK in IDLE

[Fredrik Lundh]

"Sullivan WxPyQtKinter" wrote:

> In IDLE, this py file work all right. But if I launch python
> interpretor in the command shell like this:
>
>
> C:\Documents and Settings\Xiaozhong Zheng>python "C:\Documents and
> Settings\Xiaozhong Zheng\Desktop\t.py"
>
> The interpretor would not find the file.

open("ticket.txt") means "look for ticket.txt in the current directory",
not in the directory where the PY file lives.  if you change to the Desk-
top directory before you run the Python interpreter, your script should
work as expected.

to fix this, you can

- use a full path

or

- use os.path.basedir(__file__) to get the directory where the module
  lives, and do something like

root = os.path.basedir(__file__)
ticketfile = os.path.join(root, "ticket.txt")
f = open(ticketfile)





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New python.org site

[Bertrand Mansion]

Hi,

First some introduction, my name is Bertrand Mansion, I am still
learning Python and I am new to this list. I have been developping
websites since 1995 and I use PHP since 1999. I have been contributing
to open source projects in the PHP and Apple Objective-C Cocoa
framework community. I studied business at school...

I will go straight to the point, I don't like the new Python.org
website. I didn't like the old one neither. The new one is not better
nor worse than the old one, it's just a different shell. But in my
opinion, it misses the point as well.

I am motivated to make a better website for python.org. Why ? Because
I am learning the language and I need a good resource to learn from.
In its current state, I wouldn't want to use python.org because it's
messy and doesn't match what I expect. It simply doesn't match the
quality of the language.

Note that I don't care about the logo, the colors, whatever is
personal tastes related and that's not my point. In my opinion, the
design has to fit a mission. I don't think a list of objectives was
defined prior to the new redesign. Here would be my list of objectives
for a new website, feel free to add your own:

1. Give a clear overview of what's available on python.org
2. Organize content and make it easy to access it
3. Be a gathering point for the existing community
4. Reinforce the Python image among the would-be python developers/users
5. Make it easy to add new features in the future

Each of these points would need to be extended and detailed.

Now I have a few questions:

* Is there a community interested in building a better python.org website ?
  - An active mailing list dedicated to python.org ?
  - A wiki with some improvement ideas ?

* Where is the current source code of python.org ?
  - Where are the scripts ?
  - Where are the designs ?
  - Is there a SCM available for checkout ?

* Who is currently maintaining python.org ?
  - Design
  - Code
  - Goals and objectives

* Was the last redesign a community effort or the work of one or a company ?

* How about organizing a community contest for both the logo and the
site design ?
Many people are concerned, I am pretty sure there will be a lot of
contributions, even from outside the Python community (for the
fame...). The winners could be decided by half a jury and half the
community votes. There would be a website to be done to take care of
the applications. Maybe some companies would be willing to sponsor.

Thanks for your replies,


Bertrand Mansion
Mamasam
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Re: How to best update remote compressed, encrypted archives incrementally?

[robert]

Steven D'Aprano wrote:
> On Fri, 10 Mar 2006 15:13:07 +0100, robert wrote:
> 
> 
>>Hello,
>>
>>I want to put (incrementally) changed/new files from a big file tree 
>>"directly,compressed and password-only-encrypted" to a remote backup 
>>server incrementally via FTP,SFTP or DAV  At best within a closed 
>>algorithm inside Python without extra shell tools.
> 
> 
> What do you mean by "closed algorithm"?
> 
> The only thing I can think of is you mean a secret algorithm, one which
> nobody but yourself will know. So let's get this straight... you are
> asking a public newsgroup dedicated to an open-source language for
> somebody to tell you a secret algorithm that only you will know?
> 
> Please tell me I've misunderstood.

no. I meant it terms of 'cohesive' : A Python solution without a lot of 
other tools. (Only the password has to be secret)

>>(The method should work with any protocol which allows somehow read, 
>>write & seek to a remote file.)
>>On the server and the transmission line there should never be 
>>unencrypted data.
> 
> 
> Break the job into multiple pieces. Your task is:
> 
> - transmit information to the remote server;
> 
> Can you use SSH for that? SSH will use industrial strength encryption,
> likely better than anything you can create.

Yes, sftp (=SSH) or ftp with TSL (=SSL) are good protocols. They can 
also read/navigate in a remote fila and append-to-file. But how about 
incremental+encrypted?

> - you want to update the files at the other end;
> 
> Sounds like a job for any number of already existing technologies, like
> rsync (which, by the way, already uses ssh for the encrypted transmission
> of data).

As far as I know, rsync cannot update compressed+encrypted into an 
existing file(set) ?
I any case with rsync I would have to have a duplicate of the backup 
file geometry on the local machine (consuming another magnitude of the 
file stuff itself) ?

Thats why I ask: how to get all these tasks into a cohesive encrypted 
backup solution not wasting disk space and network bandwidth?

Robert
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"RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert]

In very rare cases a program crashes (hard to reproduce) :

* several threads work on an object tree with dict's etc. in it. Items 
are added, deleted, iteration over .keys() ... ). The threads are "good" 
in such terms, that this core data structure is changed only by atomic 
operations, so that the data structure is always consistent regarding 
the application. Only the change-operations on the dicts and lists 
itself seem to cause problems on a Python level ..

* one thread periodically pickle-dumps the tree to a file:
   >>> cPickle.dump(obj, f)

"RuntimeError: dictionary changed size during iteration" is raised by 
.dump ( or a similar "..list changed ..." )

What can I do about this to get a stable pickle-dump without risiking 
execution error or even worse - errors in the pickled file ?

Is a copy.deepcopy  ( -> "cPickle.dump(copy.deepcopy(obj),f)" ) an 
atomic opertion with a guarantee to not fail?

Or can I only retry several times in case of RuntimeError?  (which would 
apears to me as odd gambling; retry how often?)

Robert


PS: Zope dumps thread exposed data structes regularly. How does the ZODB 
in Zope handle dict/list changes during its pickling operations?


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Re: Cheese Shop -> BSOL?

[Paul Boddie]

Tim Churches wrote:
> Would it be possible to rename "Cheese Shop" as "Bright Side of Life"?

Well, you could replay the conversation I gave as an example elsewhere
to see if it sounds ridiculous or not, but what we've encountered here
is the problem of whether something should be given a distinctive
identity or a derivative identity. A long time ago, and possibly
continuing to this day, people complained about how nearly every Python
package, module or program had names starting or ending with "Py" -
announcing a module in a Python newsgroup and giving it a name starting
with "Py" seemed somewhat redundant, and there was always the issue of
not being able to scan long lists of packages comfortably, just like
with all the KDE application names that start with the letter K.

But even without "the curse of Py", many people don't just choose
arbitrary names for their packages: it often makes sense to include
related technologies in the name (eg. XML, XSLT, ado, dav), or to use a
descriptive component, possibly in shortened form (eg. auth, bayes,
bio, Cal). Yes, a search will often bring forth the right resource
regardless of what it's called, but many people underestimate their own
searching skills and overestimate what other people can find via things
like Google.

Of course, programs may downplay Python as the implementation
technology because the underlying technical details are mostly
irrelevant to end-users (eg. BitTorrent, b3, Eric, Glarf), but if we
look at distinctively named packages, we can see that they often
attempt to define their own identity distinct from Python (eg.
BeautifulSoup, Dabo, DejaVu, Django, Twisted, Zope), frequently because
they seek to be the primary point of reference for developers -
developing in Twisted or Zope is more specialised than just developing
things in Python. Some of the distinctively named package names employ
metaphors and/or cultural references that possibly make them more
memorable, but they don't necessarily make the names easy to guess.

So should a service for finding Python packages have a distinct
identity? It is possible that a package index could be someone's
principal view of the Python world ("I go to Camelot to get... what is
it I get there?"), but the things that emerge from such a service
aren't just downloads that have little in common with each other.
Consequently, I don't think a descriptive name, derived from the name
of the technology, is sensibly avoided in this case.

Paul

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Re: Inconsistency of special class method lookup?

[anne . nospam01]

Thanks.

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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert]

> Is a copy.deepcopy  ( -> "cPickle.dump(copy.deepcopy(obj),f)" ) an 
> atomic opertion with a guarantee to not fail?
> 
> Or can I only retry several times in case of RuntimeError?  (which would 
> apears to me as odd gambling; retry how often?)

For an intermediate solution, I'm playing roulette:

 for i in 1,2,3:
 try:
 cPickle.dump(obj, f)
 break
 except RuntimeError,v:
 pass


I hope this works for some million years ...



> PS: Zope dumps thread exposed data structes regularly. How does the ZODB 
> in Zope handle dict/list changes during its pickling operations?
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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert]

robert wrote:

> 
>> Is a copy.deepcopy  ( -> "cPickle.dump(copy.deepcopy(obj),f)" ) an 
>> atomic opertion with a guarantee to not fail?
>>
>> Or can I only retry several times in case of RuntimeError?  (which 
>> would apears to me as odd gambling; retry how often?)
> 
> 
> For an intermediate solution, I'm playing roulette:
> 
> for i in 1,2,3:
> try:
> cPickle.dump(obj, f)
> break
> except RuntimeError,v:
> pass
> 

hmm..

 for i in 1,2,3:
 try:
 cPickle.dump(obj, f)
 break
 except RuntimeError,v:
 f.seek(0);f.truncate(0)


Meanwhile I think this is a bug of cPickle.dump: It should use .keys() 
instead of free iteration internally, when pickling elementary dicts. 
I'd file a bug if no objection.

Robert


> I hope this works for some million years ...
> 
> 
> 
>> PS: Zope dumps thread exposed data structes regularly. How does the 
>> ZODB in Zope handle dict/list changes during its pickling operations?
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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[Felipe Almeida Lessa]

Em Sáb, 2006-03-11 às 12:49 +0100, robert escreveu:
> Meanwhile I think this is a bug of cPickle.dump: It should use .keys() 
> instead of free iteration internally, when pickling elementary dicts. 
> I'd file a bug if no objection.

AFAICS, it's a problem with your code. You should lock your object while
using it. That's what Threading.Lock is supposed to work for. If you
want to use threads, you have to know in what parts of your code there
should be locks.

Cya,
Felipe.

-- 
"Quem excele em empregar a força militar subjulga os exércitos dos
outros povos sem travar batalha, toma cidades fortificadas dos outros
povos sem as atacar e destrói os estados dos outros povos sem lutas
prolongadas. Deve lutar sob o Céu com o propósito primordial da
'preservação'. Desse modo suas armas não se embotarão, e os ganhos
poderão ser preservados. Essa é a estratégia para planejar ofensivas."

  -- Sun Tzu, em "A arte da guerra"

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Re: How to best update remote compressed, encrypted archives incrementally?

[Steven D'Aprano]

On Sat, 11 Mar 2006 11:46:24 +0100, robert wrote:

>> Sounds like a job for any number of already existing technologies, like
>> rsync (which, by the way, already uses ssh for the encrypted transmission
>> of data).
> 
> As far as I know, rsync cannot update compressed+encrypted into an 
> existing file(set) ?
> I any case with rsync I would have to have a duplicate of the backup 
> file geometry on the local machine (consuming another magnitude of the 
> file stuff itself) ?

Let me see if I understand you.

On the remote machine, you have one large file, which is compressed and
encrypted. Call the large file "Archive". Archive is made up of a number
of virtual files, call them A, B, ... Z. Think of Archive as a compressed
and encrypted tar file.

On the local machine, you have some, but not all, of those smaller
files, let's say B, C, D, and E. You want to modify those smaller files,
compress them, encrypt them, transmit them to the remote machine, and
insert them in Archive, replacing the existing B, C, D and E.

Is that correct?

> Thats why I ask: how to get all these tasks into a cohesive encrypted 
> backup solution not wasting disk space and network bandwidth?

What's your budget for developing this solution? $100? $1000? $10,000?
Stop me when I get close. Remember, your time is money, and if you are a
developer, every hour you spend on this is costing your employer anything
from AUD$25 to AUD$150. (Of course, if you are working for yourself, you
might value your time as Free.)

If you have an unlimited budget, you can probably create a solution to do
this, keeping in mind that compressed/encrypted and modify-in-place
*rarely* go together. 

If you have a lower budget, I'd suggest you drop the "single file"
requirement. Hard disks are cheap, less than an Australian dollar a
gigabyte, so don't get trapped into the false economy of spending $100 of
developer time to save a gigabyte of data. Using multiple files makes it
*much* simpler to modify-in-place: you simply replace the modified file.
Of course the individual files can be compressed and encrypted, or you can
use a compressed/encrypted file system. 

Lastly, have you considered that your attempted solution is completely the
wrong way to solve the problem? If you explain _what_ you are wanting to
do, rather than _how_ you want to do it, perhaps there is a better way.


-- 
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why "g".count('')==2 ?

[ygao]

my question is as title!
thanks!

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Re: why "g".count('')==2 ?

[Fredrik Lundh]

"ygao" wrote:

> my question is as title!

my answer as code:

>>> s = "g"
>>> t = ""
>>> s[0:0+len(t)] == t
True
>>> s[1:1+len(t)] == t
True





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Re: %r

[Fredrik Lundh]

Blackbird wrote:

> By "cargo cult programming", do you mean actually *running* the code?

no, I mean basing your mental model of something on distant observations
of superficial (or accidental) artifacts (like the perceived similarity between
the output from repr() and the raw string literal syntax), rather than on an
attempt to understand what's really going on, and what causes what.

or something like that.





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Re: why "g".count('')==2 ?

[Steven D'Aprano]

On Sat, 11 Mar 2006 13:37:05 +0100, Fredrik Lundh wrote:

> "ygao" wrote:
> 
>> my question is as title!
> 
> my answer as code:
> 
 s = "g"
 t = ""
 s[0:0+len(t)] == t
> True
 s[1:1+len(t)] == t
> True


Or in other words, imagine that Python is walking the string looking to
match the target. The empty string matches the boundary of every character
with the next character, or in other words, for a string s of length N,
s.count('') will equal N+1.

I'm not sure what to describe this surprising result as. It isn't a bug;
it isn't even really a gotcha. I guess the best description is that it is
just a surprising, but logical, result.

(Well, I was surprised -- but I can't fault the logic.)


-- 
Steven.

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Re: Can not find a file in CMD model python when everything is OK in IDLE

[Sullivan WxPyQtKinter]

I see. I once was a VB programmer. In VB, the current directory is
always set to where the module locates before it runs.

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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[EleSSaR^]

robert si è profuso/a a scrivere su comp.lang.python tutte queste
elucubrazioni: 

[cut]

I don't know what's your code like, but a similar error occurred in some of
my software and it was my fault indeed. I think you should either use a
lock, or implement a deepcopy method of your own.

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Re: Cheese Shop -> BSOL?

[Kay Schluehr]

Paul Boddie wrote:
> Tim Churches wrote:
> > Would it be possible to rename "Cheese Shop" as "Bright Side of Life"?
>
> Well, you could replay the conversation I gave as an example elsewhere
> to see if it sounds ridiculous or not, but what we've encountered here
> is the problem of whether something should be given a distinctive
> identity or a derivative identity. A long time ago, and possibly
> continuing to this day, people complained about how nearly every Python
> package, module or program had names starting or ending with "Py" -
> announcing a module in a Python newsgroup and giving it a name starting
> with "Py" seemed somewhat redundant, and there was always the issue of
> not being able to scan long lists of packages comfortably, just like
> with all the KDE application names that start with the letter K.
>
> But even without "the curse of Py", many people don't just choose
> arbitrary names for their packages: it often makes sense to include
> related technologies in the name (eg. XML, XSLT, ado, dav), or to use a
> descriptive component, possibly in shortened form (eg. auth, bayes,
> bio, Cal). Yes, a search will often bring forth the right resource
> regardless of what it's called, but many people underestimate their own
> searching skills and overestimate what other people can find via things
> like Google.
>
> Of course, programs may downplay Python as the implementation
> technology because the underlying technical details are mostly
> irrelevant to end-users (eg. BitTorrent, b3, Eric, Glarf), but if we
> look at distinctively named packages, we can see that they often
> attempt to define their own identity distinct from Python (eg.
> BeautifulSoup, Dabo, DejaVu, Django, Twisted, Zope), frequently because
> they seek to be the primary point of reference for developers -
> developing in Twisted or Zope is more specialised than just developing
> things in Python. Some of the distinctively named package names employ
> metaphors and/or cultural references that possibly make them more
> memorable, but they don't necessarily make the names easy to guess.
>
> So should a service for finding Python packages have a distinct
> identity? It is possible that a package index could be someone's
> principal view of the Python world ("I go to Camelot to get... what is
> it I get there?"), but the things that emerge from such a service
> aren't just downloads that have little in common with each other.
> Consequently, I don't think a descriptive name, derived from the name
> of the technology, is sensibly avoided in this case.
>
> Paul

The problem I have with the cheese-shop is less a naming but a
usability issue. In some commercial projects that involve Python I
already integrated SQLite as a local database for storing and
retrieving all kind of configuration data as well as session data,
failure statistics etc. I also extended a Python console in order to
send SQL commands directly using this syntax "$ select * from reports
where...". I should mention that this kind of integration was one of
the most acknowledged features by those who where Python sceptics. I
wonder if creating a database client, integreting it with a Python
console and shipping it with a Python setup would not leave behind all
other solutions in the field? BTW I'm not only intererested in the
functionality of a package but how well it performs how well it is
tested etc. The packages checked into the cheese-shop obtain already a
rough classification. If classification schemes become more usable it
is likely that they could be extended. 

Kay

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Re: Can not find a file in CMD model python when everything is OK in IDLE

[Sullivan WxPyQtKinter]

I see. I once was a VB programmer. In VB, the current directory is
always set to where the module locates before it runs.

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Re: why use special config formats?

[gangesmaster]

> Huh? You think a competent sys admin can't learn enough Python to hack
> your pickled file?
>
> Binary configs only keep out legitimate users who don't have the time or
> ability to learn how to hack the binary format. Black hats and power users
> will break your binary format and hack them anyway.

then you dont know what pickle is. pickle code is NOT python bytecode.
it's a bytecode they made in order to represent objects. you cannot
"exploit" in in the essence of running arbitrary code, unless you find
a bug in the pickle module. and that's less likely than you find a bug
in the parser of the silly config file formats you use.

i'm not hiding the configuration in "binary files", that's not the
point. pickle is just more secure by definition.

aah. you all are too stupid.


-tomer

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Re: New python.org site

[Thorsten Kampe]

* Bertrand Mansion (2006-03-11 10:23 +)
> I will go straight to the point, I don't like the new Python.org
> website.

Well, I like it.

> I didn't like the old one neither.

Yeah, the old one was a mess.

> The new one is not better nor worse than the old one, it's just a
> different shell. But in my opinion, it misses the point as well.
 
> I am motivated to make a better website for python.org. Why ? Because
> I am learning the language and I need a good resource to learn from.
> In its current state, I wouldn't want to use python.org because it's
> messy and doesn't match what I expect. It simply doesn't match the
> quality of the language.
> 
> Note that I don't care about the logo, the colors, whatever is
> personal tastes related and that's not my point. In my opinion, the
> design has to fit a mission. I don't think a list of objectives was
> defined prior to the new redesign. Here would be my list of objectives
> for a new website, feel free to add your own:
> 
> 1. Give a clear overview of what's available on python.org
> 2. Organize content and make it easy to access it
> 3. Be a gathering point for the existing community
> 4. Reinforce the Python image among the would-be python developers/users
> 5. Make it easy to add new features in the future

Good points.
 
> Each of these points would need to be extended and detailed.
> 
> Now I have a few questions:
> [...]

There have recently been threads here about the website. Maybe the
discussion there gives you some information needed:

* 
http://groups.google.com/group/comp.lang.python/browse_thread/thread/f4c1585fe379d8ad/11fd0062787e374c?tvc=2&q=group%3Acomp.lang.python+insubject%3Apython.org&hl=en#11fd0062787e374c
* 
http://groups.google.com/group/comp.lang.python/browse_thread/thread/23c5ee82f22757f3/2696c44b8385a8e8?tvc=2&q=group%3Acomp.lang.python+insubject%3Apython.org&hl=en#2696c44b8385a8e8
* 
http://groups.google.com/group/comp.lang.python/browse_thread/thread/330af3b245145f7e/667bb15d53f0c555?tvc=2&q=group%3Acomp.lang.python+insubject%3Apython.org&hl=en#667bb15d53f0c555
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Re: why use special config formats?

[gangesmaster]

>> Why is the first uglier than the second?
YES THATS THE POINT. PYTHON CAN BE USED JUST LIKE A CONFIG FILE.

and if your users did
timeout = "300"
instead of
timeout = 300

then either your config parser must be uber-smart and all-knowing, and
check the types of key-value pairs, or your server would crash. either
way is bad, and i prefer crash-on-use then
know-everything-and-check-at-the-parser-level.



good night,
-tomer

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Re: why no block comments in Python?

[Roy Smith]

In article <[EMAIL PROTECTED]>,
 "Jonathan Gardner" <[EMAIL PROTECTED]> wrote:

> Warby wrote:
> > ...and I forgot to mention that the output of grep and diff is far more
> > understandable in the absence of block comments!
> 
> Which is why people do this /anyway/. (Kind of makes block comments
> pointless, doesn't it?
> 
> /* This is a 
>  * really
>  * really
>  * long
>  * block comment */

Habit left over from the C days.  It was the only way of making a block 
comment stand out visually.  C++ has // comments, just like Python has #, 
but old habits die hard.
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Re: New python.org site

[Bertrand Mansion]

On 3/11/06, Thorsten Kampe <[EMAIL PROTECTED]> wrote:

> There have recently been threads here about the website. Maybe the
> discussion there gives you some information needed:
>
> * 
> http://groups.google.com/group/comp.lang.python/browse_thread/thread/f4c1585fe379d8ad/11fd0062787e374c?tvc=2&q=group%3Acomp.lang.python+insubject%3Apython.org&hl=en#11fd0062787e374c
> * 
> http://groups.google.com/group/comp.lang.python/browse_thread/thread/23c5ee82f22757f3/2696c44b8385a8e8?tvc=2&q=group%3Acomp.lang.python+insubject%3Apython.org&hl=en#2696c44b8385a8e8
> * 
> http://groups.google.com/group/comp.lang.python/browse_thread/thread/330af3b245145f7e/667bb15d53f0c555?tvc=2&q=group%3Acomp.lang.python+insubject%3Apython.org&hl=en#667bb15d53f0c555

I have read those, they look like Slashdot comments where you get some
people trying to post a good joke... They don't answer my simple
questions:

1. Who is maintaining python.org ?

2. Where is the site code/design available ?

3. Is the last redesign a solo or a community effort ?
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Re: Why property works only for objects?

[Bruno Desthuilliers]

Michal Kwiatkowski a écrit :
> Bruno Desthuilliers napisał(a):
> 
>>>Let me understand it clearly. If I change __class__ of an object,
>>>existing attributes (so methods as well) of an object are still
>>>accessible the same way and don't change its values. Only resolution of
>>>attributes/methods not found in object is changed, as it uses new
>>>version of __class__ to lookup names. Is this right?
>>
>>Attributes, yes. Not methods. Methods are looked up in the class.
> 
> 
> My experience shows exactly the opposite. Any attribute/method you try
> to access is first looked up in object dictionary, then inside class
> definition.

Yes, that's what I said.

You wrote:
"""
existing attributes (so methods as well) of an object are still
accessible the same way and don't change its values
"""

Attributes (I mean instance attributes) living in the object's dict, 
they aren't impacted by the runtime class change. Methods being in the 
most common case (I'd say > 99.9 %) defined *in the class*, if you 
change the class of an object, this is very likely to impact resolution 
of methods lookup.

Now I agree that the statement "methods are looked up in the class" is 
wrong. Methods are of course first looked up in the object, then in the 
class. But the case of a method living in the object's dict is not that 
common...
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Re: New python.org site

[skip]

Bertrand> 1. Who is maintaining python.org ?

Start with mail to [EMAIL PROTECTED]

Bertrand> 2. Where is the site code/design available ?

It's in Subversion.  Start here:

http://psf.pollenation.net/

Bertrand> 3. Is the last redesign a solo or a community effort ?

Small community.  One person did the bulk of the work.  A sprint at the
recent PyCon a week ago finished many things off and got a lot of content
converted from the old site to the new.  Stuff that hasn't yet been
converted and hasn't had proper redirects set up falls through to the old
site (that is obvious when it happens).  Hopefully the number of pages where
that occurs is dropping.

Now the developers are tackling a lot of bug reports, converting the last
content and fixing redirect problems.

The conversion has been particularly challenging because not only was the
site redesigned from an appearance standpoint, it was restructured (almost
all content got new URLs) and a new content management system was written to
support the content (http://pyramid.pollenation.net/).  Oh, the Subversion
repository holding the content changed as well.

Skip
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Re: How to best update remote compressed, encrypted archives incrementally?

[robert]

Steven D'Aprano wrote:


> Let me see if I understand you.
> 
> On the remote machine, you have one large file, which is compressed and
> encrypted. Call the large file "Archive". Archive is made up of a number
> of virtual files, call them A, B, ... Z. Think of Archive as a compressed
> and encrypted tar file.
> 
> On the local machine, you have some, but not all, of those smaller
> files, let's say B, C, D, and E. You want to modify those smaller files,
> compress them, encrypt them, transmit them to the remote machine, and
> insert them in Archive, replacing the existing B, C, D and E.
> 
> Is that correct?

Yes, that is it. In addition a possiblity for (fast) comparison of 
individual files would be optimal.

>>Thats why I ask: how to get all these tasks into a cohesive encrypted 
>>backup solution not wasting disk space and network bandwidth?
> 
> What's your budget for developing this solution? $100? $1000? $10,000?
> Stop me when I get close. Remember, your time is money, and if you are a
> developer, every hour you spend on this is costing your employer anything
> from AUD$25 to AUD$150. (Of course, if you are working for yourself, you
> might value your time as Free.)
> 
> If you have an unlimited budget, you can probably create a solution to do
> this, keeping in mind that compressed/encrypted and modify-in-place
> *rarely* go together. 
> 
> If you have a lower budget, I'd suggest you drop the "single file"
> requirement. Hard disks are cheap, less than an Australian dollar a
> gigabyte, so don't get trapped into the false economy of spending $100 of
> developer time to save a gigabyte of data. Using multiple files makes it
> *much* simpler to modify-in-place: you simply replace the modified file.
> Of course the individual files can be compressed and encrypted, or you can
> use a compressed/encrypted file system. 
> 
> Lastly, have you considered that your attempted solution is completely the
> wrong way to solve the problem? If you explain _what_ you are wanting to
> do, rather than _how_ you want to do it, perhaps there is a better way.

So, there seems to be a big barrier for that task, when encryption is on 
the whole archive. A complex block navigation within a block cipher 
would be required, and obviously there is no such (handy) code already 
existing. Or is there a encryption/decryption method which you can can 
use like a file pipe _and_ which supports 'seek'?

Thus, a simple method would use a common treshold timestamp or 
archive-bits and create multiple archive slices. (Instable when the file 
set is dynamic and older files are copied to the tree.)

2 nearly optimal solutions which allows comparing individual files

1st:
+ an (s)ftp(s)-to-zip/tar bridge seems to be possible. E.g. by hooking 
ZipFile to use a virtual self.fp
+ the files would be individually encrypted by a password
- an external tool like "gpg -c" is necessary; (or is there a good 
encryption with a native python module? Is PGP (password only) possible 
with a native python module? )
- the filenames would be visible

2nd:
+ manage a dummy file-tree locally for speedy comparision (with 0-length 
files)
+ create encrypted archive slices for upload with iterated filenames
- an external tool like "gpg -c" is necessary
- extra file tree or file attribute database
- unrolling status from multiple archive slices is arduous

Robert
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Re: why use special config formats?

[Fredrik Lundh]

"gangesmaster" wrote:

> > Binary configs only keep out legitimate users who don't have the time or
> > ability to learn how to hack the binary format. Black hats and power users
> > will break your binary format and hack them anyway.
>
> then you dont know what pickle is. pickle code is NOT python bytecode.
> it's a bytecode they made in order to represent objects. you cannot
> "exploit" in in the essence of running arbitrary code

import pickle
print pickle.loads("cos\nsystem\np0\n(S'echo really?'\np1\ntp2\nRp3\n.")





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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert]

Felipe Almeida Lessa wrote:

> Em Sáb, 2006-03-11 às 12:49 +0100, robert escreveu:
> 
>>Meanwhile I think this is a bug of cPickle.dump: It should use .keys() 
>>instead of free iteration internally, when pickling elementary dicts. 
>>I'd file a bug if no objection.
> 
> 
> AFAICS, it's a problem with your code. You should lock your object while
> using it. That's what Threading.Lock is supposed to work for. If you
> want to use threads, you have to know in what parts of your code there
> should be locks.

99.99% no. I would have to use a lock everywhere, where I add or remove 
something into a dict or list of the struct. Thats not the purpose of 
big thread locks. Such simple operations are already atomic by the 
definition of Python - and thanks to the global interpreter lock. 
(Otherwise I would leave the Python language, God beware ... :-) )

I'm of course aware, where to use locks for resons of the application. 
But this is an issue on Python level. And it can be solved gracly and 
simple in Python  - I guess:

If cPickle.dump (and maybe also copy/deepcopy?) is corrected to work 
atomic on dicts (use .keys()) and list-copies or locks python threads) 
the problem is solved gracely and generally.

Robert







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Re: put multiple condition in if statement

[Bruno Desthuilliers]

[EMAIL PROTECTED] a écrit :
> Hi,
> 
> How can I put multiple condition in if statement?

With "and"s and "or"s.

> 
> I try this, but I can't get that to work.
 >
> if ( (str != " ") && (str != "") ):


FWIW, I would not hope a type to be equal to a string !-)


> Any help is appreciated.

"doesn't work" is the most useless possible description of a problem. As 
a general rule, please:
- post the minimal running code that exhibit the problem
- clearly state the result you hoped and the result you got.

Also, don't use builtin names as identifier. "str" is the string type, 
so using "str" as an identifier will shadow the str type.

And, finally, you don't even need multiple conditions here - this should 
be enough (using 'my_string' instead of 'str'):

if my_string.strip() :
   ...

In Python, an empty sequence (strings, lists, tuples, ...), an empty 
mapping (dict, ...), the integer 0 and the float 0.0 are all evalued to 
False in a boolean expression. So any non-empty string evals to True. 
The method strip() of type str returns a copy of the string with leading 
and trailing whitespaces removed, so " ".strip() will return "".

HTH
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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[robert]

EleSSaR^ wrote:

> robert si è profuso/a a scrivere su comp.lang.python tutte queste
> elucubrazioni: 
> 
> [cut]
> 
> I don't know what's your code like, but a similar error occurred in some of
> my software and it was my fault indeed. I think you should either use a
> lock, or implement a deepcopy method of your own.

100s of locks? no (see other message). It should be

own deepcopy: thus, do you already know if the existing deepcopy has the 
same problem as cPickle.dump ?(as the problem araises rarely, it is 
difficult for me to test it out)

Robert

PS: how does ZODB work with this kind of problem? I thought is uses cPickle?
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Re: Which GUI toolkit is THE best?

[David Boddie]

Alan Franzoni wrote:

> FLTK was interesting but seems to lack maintenance and support,

Looking at the News section of the project's home page, I can see
that updates were few and far between in 2004 and 2005, but the
action seems to have picked up again since:

  http://pyfltk.sourceforge.net/#news

> pyQT is a bit 'unfree' for most uses.

"Unfree" as in the opposite of freedom, or "unfree" as in the price of
beer?

PyQt for Qt 3 is available under the GNU General Public License on
Mac OS X and Linux. Since Qt 4 can be used under the GPL on all
platforms, you'll even be able to write software on Windows with PyQt4
that's licensed under a GPL-compatible license.

  FAQ: http://www.riverbankcomputing.co.uk/pyqt/faq.php
  Roadmap: http://www.riverbankcomputing.co.uk/pyqt/roadmap.php

> Tkinter is quite old stuff.

But actively supported and promoted:

  http://wiki.python.org/moin/TkInter

And I'm sure there are plenty of other solutions that deserve to be
mentioned:

  http://wiki.python.org/moin/GuiProgramming

David

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Re: why use special config formats?

[Steve Holden]

gangesmaster wrote:
>>Huh? You think a competent sys admin can't learn enough Python to hack
>>your pickled file?
>>
>>Binary configs only keep out legitimate users who don't have the time or
>>ability to learn how to hack the binary format. Black hats and power users
>>will break your binary format and hack them anyway.
> 
> 
> then you dont know what pickle is. pickle code is NOT python bytecode.
> it's a bytecode they made in order to represent objects. you cannot
> "exploit" in in the essence of running arbitrary code, unless you find
> a bug in the pickle module. and that's less likely than you find a bug
> in the parser of the silly config file formats you use.
> 
> i'm not hiding the configuration in "binary files", that's not the
> point. pickle is just more secure by definition.
> 
> aah. you all are too stupid.
> 
Great way to win an argument. Pity we aren't as intelligent as you ...

regards
  Steve
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Re: why use special config formats?

[Sybren Stuvel]

gangesmaster enlightened us with:
> YES THATS THE POINT. PYTHON CAN BE USED JUST LIKE A CONFIG FILE.

AND CAN ALSO BE MISUSED AND HARDER TO USE THAN A SIMPLE CONFIG FILE.
Get it into your thick head that you're plain wrong here.

Sybren
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safety labels off of everything and let the problem solve itself? 
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Re: why use special config formats?

[Rick Zantow]

"gangesmaster" <[EMAIL PROTECTED]> wrote in
news:[EMAIL PROTECTED]: 

> aah. you all are too stupid.

-1 QOTW.

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rzed

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Re: How to best update remote compressed, encrypted archives incrementally?

[Steven D'Aprano]

On Sat, 11 Mar 2006 16:09:22 +0100, robert wrote:

>> Lastly, have you considered that your attempted solution is completely the
>> wrong way to solve the problem? If you explain _what_ you are wanting to
>> do, rather than _how_ you want to do it, perhaps there is a better way.
> 
> So, there seems to be a big barrier for that task, when encryption is on 
> the whole archive. A complex block navigation within a block cipher 
> would be required, and obviously there is no such (handy) code already 
> existing. Or is there a encryption/decryption method which you can can 
> use like a file pipe _and_ which supports 'seek'?

[snip]

Let's try again: rather than you telling us what technology you want to
use, tell us what your aim is. I suspect you are too close to the trees to
see the forest -- you are focusing on the fine detail. Let's hear the big
picture: what is the problem you are trying to solve? Because, frankly, as
far as I can see, the solution you are looking for doesn't exist. But
maybe I'm too far from the forest to see the individual trees.

"I need encryption that supports seek" -- no, that's you telling us _how_
you want to solve your problem.

Perhaps you can tick some/all of the following requirements:

- low bandwidth usage when updating the remote site

- transmission needs to be secure

- data on the remote site needs to be secure in case of theft or break-ins

- remote site is under the control of untrusted parties; 
or remote site is trusted

- remote site is an old machine with limited processing power and very
small disk storage; 
or remote site can be any machine we choose

- local site needs to run Windows/Macintosh/Linux/BSD/all of the above

- remote site runs on Windows/Macintosh/Linux/BSD/anything we like

- we are updating text files/binary files 

- anything else you can tell us about the nature of your problem 



-- 
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Re: why use special config formats?

[Steven D'Aprano]

On Sat, 11 Mar 2006 05:49:38 -0800, gangesmaster wrote:

>>> Why is the first uglier than the second?
> YES THATS THE POINT. PYTHON CAN BE USED JUST LIKE A CONFIG FILE.
> 
> and if your users did
> timeout = "300"
> instead of
> timeout = 300
> 
> then either your config parser must be uber-smart and all-knowing, and
> check the types of key-value pairs, or your server would crash. either
> way is bad, and i prefer crash-on-use then
> know-everything-and-check-at-the-parser-level.

Well, I think this puts a new light on the argument from Tomer: he'd
prefer his server to crash than to spend some time validating his data.

Would you mind telling us what software you've been involved in writing,
so we know what software to avoid?


-- 
Steven.

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What has become of the Python 2004 papers?

[Andrew Koenig]

http://www.python.org/community/pycon/dc2004 seems to have vanished...


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Re: New python.org site

[Luis M. González]

I wouldn't want to sound like I'm criticizing other people's work.
To those who offered their time to create this site, which is quite an
improvement over the old one, thank you!

However, I like the idea of a contest. Both for the site and for the
logo.
Perhaps something cool could come up from the new crop of
Django/TurboGears fans our there...

For many people, these things may seem superfluos or not important at
all, but good marketing and good design helps to create an image and an
identity.

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Re: why use special config formats?

[Fredrik Lundh]

> > YES THATS THE POINT. PYTHON CAN BE USED JUST LIKE A CONFIG FILE.
>
> AND CAN ALSO BE MISUSED AND HARDER TO USE THAN A SIMPLE CONFIG FILE.
> Get it into your thick head that you're plain wrong here.

comp.lang.python sure isn't what it used to be :-(





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Old Python Logo

[Spinchange]

Can someone post a link or email me an image of the old Python logo?
I'd like to save a copy of it, I rather liked it - very retro.

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Re: Old Python Logo

[Fredrik Lundh]

"Spinchange" wrote:

> Can someone post a link or email me an image of the old Python logo?
> I'd like to save a copy of it, I rather liked it - very retro.

the dot matrix logo ?

you can get a copy from this page:

http://pydotorg.dyndns.org:8000/PythonOrg.html





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Re: why "g".count('')==2 ?

[Terry Reedy]

For the same reason as
>>> "".count("")
1
>>> "ab".count("")
3

This is counting slice positions, which is one more that the length of the 
string.



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Re: why "g".count('')==2 ?

[Felipe Almeida Lessa]

Em Sáb, 2006-03-11 às 04:25 -0800, ygao escreveu:
> my question is as title!
> thanks!

Forget it. Just look:

$ python2.4 -mtimeit '"g".count("")'
100 loops, best of 3: 0.516 usec per loop
$ python2.4 -mtimeit 'len("g")+1'
100 loops, best of 3: 0.26 usec per loop


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outros povos sem travar batalha, toma cidades fortificadas dos outros
povos sem as atacar e destrói os estados dos outros povos sem lutas
prolongadas. Deve lutar sob o Céu com o propósito primordial da
'preservação'. Desse modo suas armas não se embotarão, e os ganhos
poderão ser preservados. Essa é a estratégia para planejar ofensivas."

  -- Sun Tzu, em "A arte da guerra"

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Re: How to best update remote compressed, encrypted archives incrementally?

[robert]

Steven D'Aprano wrote:

> On Sat, 11 Mar 2006 16:09:22 +0100, robert wrote:
> 
> 
>>>Lastly, have you considered that your attempted solution is completely the
>>>wrong way to solve the problem? If you explain _what_ you are wanting to
>>>do, rather than _how_ you want to do it, perhaps there is a better way.
>>
>>So, there seems to be a big barrier for that task, when encryption is on 
>>the whole archive. A complex block navigation within a block cipher 
>>would be required, and obviously there is no such (handy) code already 
>>existing. Or is there a encryption/decryption method which you can can 
>>use like a file pipe _and_ which supports 'seek'?
> 
> 
> [snip]
> 
> Let's try again: rather than you telling us what technology you want to
> use, tell us what your aim is. I suspect you are too close to the trees to
> see the forest -- you are focusing on the fine detail. Let's hear the big
> picture: what is the problem you are trying to solve? Because, frankly, as
> far as I can see, the solution you are looking for doesn't exist. But
> maybe I'm too far from the forest to see the individual trees.
> 
> "I need encryption that supports seek" -- no, that's you telling us _how_
> you want to solve your problem.
> 
> Perhaps you can tick some/all of the following requirements:
> 
> - low bandwidth usage when updating the remote site
> 
> - transmission needs to be secure
> 
> - data on the remote site needs to be secure in case of theft or break-ins
> 
> - remote site is under the control of untrusted parties; 
> or remote site is trusted
> 
> - remote site is an old machine with limited processing power and very
> small disk storage; 
> or remote site can be any machine we choose
> 
> - local site needs to run Windows/Macintosh/Linux/BSD/all of the above
> 
> - remote site runs on Windows/Macintosh/Linux/BSD/anything we like
> 
> - we are updating text files/binary files 
> 
> - anything else you can tell us about the nature of your problem 

The main requirement is, that it has to be become a cohesive, reusable, 
portable (FTP/SFTP standard) functionality as mentioned in the OP. A 
Python module at best. For integration in a bigger Python app. not a 
one-time admin hack with a bunch of tools to be fiddled together on each 
user machine. So the 'how' is mostly =='what'. Its a Python question so far.

The last 2 methods I mentioned already are maybe a way to a compromise, 
  (if integrated one-stream encryption cannot be managed)

The only issue remaining: A native Python module for pgp-(pwd 
only)-encryption or another kind of good (commonly supported) 
encryption. ZIP2-encryption itself seems to be too weak? (Still so in 
recent ZIP formats? what about the mode of 7zip etc?)  But I found no 
python modules for either.

http://www.amk.ca/python/code/gpg  just calls into an external gpg 
installation.

Can the functionality of "gpg -c"  maybe fiddled together with PyCrypto
easily ?  (variable length key/pwd only - no public key stuff required)

And what about ZIP password-only encryption itself?  Are there maybe any 
usable improvents ?

And: when there are many files encrypted with the same password (both 
PGP and ZIP), will this decrease the strength of encryption?

Robert
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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[Alex Martelli]

robert <[EMAIL PROTECTED]> wrote:
   ...
> 99.99% no. I would have to use a lock everywhere, where I add or remove
> something into a dict or list of the struct. Thats not the purpose of
> big thread locks. Such simple operations are already atomic by the 
> definition of Python - and thanks to the global interpreter lock. 
> (Otherwise I would leave the Python language, God beware ... :-) )

You have misread the Python Language Reference -- if you can give the
URL on which you have read any such promise of atomicity, I will be glad
to fix the docs to make that unambiguous.

There is no such promise (there may be implementation accidents in some
specific implementation which happen to make some operation atomic, but
NO guarantee even there that the next bugfix won't break that).

Farwell and best of luck in finding other languages which support
threads in a way that is more to your liking than Python -- maybe Ruby
suits you, I don't know for sure though.


Alex
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Re: Cheese Shop -> BSOL?

[Scott David Daniels]

Just wrote:
> In article <[EMAIL PROTECTED]>,
>  Dennis Lee Bieber <[EMAIL PROTECTED]> wrote:
>> On Sat, 11 Mar 2006 13:30:43 +1100, Tim Churches
>> <[EMAIL PROTECTED]> declaimed the following in comp.lang.python:
>>> Would it be possible to rename "Cheese Shop" as "Bright Side of Life"?
>>  I think I'd prefer "The Larch"...
>>  Or just "SPAM" ( Python  Modules ?)
> Standard Python Archive (of) Modules?

Some of these names are so much fun that I'd be happy to have
 http://cheeseshop.python.org
 http://larch.python.org
and http://spam.python.org

all get to the same page.

--Scott David Daniels
[EMAIL PROTECTED]
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Python Love :)

[mwt]

I've only been goofing around with Python for about a month now, but
already I am in love.
I never get that feeling -- so common with Java -- that I'm swimming
upstream, struggling to force the language to do what I want.
Python makes it feel effortless and easy.

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Re: What has become of the Python 2004 papers?

[skip]

Andrew> http://www.python.org/community/pycon/dc2004 seems to have
Andrew> vanished...

Andrew,

Try here:

http://us.pycon.org/zope/original/pycon/pastevents/dc2004

I found it by going to http://www.python.org/community/pycon/ then clicking
the 2004 link in the Past Conferences section.

I believe the plan is to move most/all the PyCon-related stuff to the
pycon.org domain, though I'm not certain about that.

Skip

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Re: Cheese Shop -> BSOL?

[Michael Tobis]

I like cheeseshop just fine, but have been a Monty Python fan since
they appeared on the CBC in, I think, 1969. I'm one of those people who
is always surprised when a MP bon mot is greeted with confusion and the
suspicion that I have finally lost my mind altogether. So...

If we are moving to the snake motif (which probably would be better
marketing):

"Pythons lay eggs which they arrange in a pile. They coil around the
pile until all eggs have hatched. Since pythons cannot regulate their
internal body temperature, they cannot incubate their eggs per se;
instead, they raise the temperature of their eggs by small movements of
their body-essentially, they "shiver". This is one of only a few
documented cases of parental behaviour in snakes."
--Wikipedia article "python"

Pythons build no nests. Their eggs are found in coils. coil.python.org
?

Tadpoles ( http://python.org/images/python-logo.gif ) are immature
frogs. If we keep the logo, we can change the name of the language to
"frog". Then the eggs would be found in lilypad.frog.org . I personally
do not like this choice but it would have the virtue of consistency.
(Did I mention that I don't like the logo?)

mt

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Python source cross reference doc generator?

[Harry Fuecks]

Hi All,

Wondering if a tool exists to generate "cross reference" documentation
for Python code bases?

Particularly after something like phpxref -
http://phpxref.sourceforge.net/ : written in Perl, scans a bunch of
PHP scripts and generates HTML output that allows you to see all the
classes / methods / functions / variables defined and (what I'm
interested in) where they are referenced. Essentially something like
API docs but with the addition of being able to see who's using a
particular method

Is there anything like this for Python? Have done much looking without success.

Many thanks.
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Re: Cheese Shop -> BSOL?

[Torsten Bronger]

Hallöchen!

"Michael Tobis" <[EMAIL PROTECTED]> writes:

> [...]
>
> Pythons build no nests. Their eggs are found in coils. coil.python.org
> ?

Better eggs.python.org.  Would support the spread of the new file
format, too.

Tschö,
Torsten.

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Advice for creating a web app

[Jumping until blue]

I'm confused ... and need some advice

Here is what I want to do:

I have a number of files, mostly text files formatted using Markdown
syntax but also pdfs and other types of files, that are stored in a
folder hierarchy and I want to develop a web application where I can
brows, view and search these files. The documents can be
cross-linked.

Currently I use a basic CGI to view/format the markdown files but I
don't know if I should continue to make my own system or if I should
take advantage of some existing framework.

My requirements are:

+   It should work with the text files I have in my
hierarchy (so a system that stores everything
in a database is out of the question)

+   I want to be able to copy the folder hierarchy
to a memory stick and run my system on another
computer without having to install any software
(I'm thinking of using something like Movable 
Python). I'll mostly be running this on Macs
but would like to have the option to run it
on Windows/Linux

+   Searching should be fairly fast

+   I should be able to edit the text files using a
standard text editor without messing up the system.

+   I will use subversion to keep different computers
in sync.

So my question is: should I use some existing framwork? and if so,
which ones should I look at? TurboGears, Django, etc seem to be much
too elaborate for my modest needs.

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Re: How to pop random item from a list?

[Andrew Gwozdziewycz]

On Mar 11, 2006, at 11:21 AM, Peter Otten wrote:

> Am Freitag, 10. März 2006 19:38 schrieben Sie:
>
 item = mylist.pop(random.randint(0,len(mylist)))
>>>
>>> This is broken because randint(a, b) may return b.
>>> I prefer randrange(len(mylist)) over randint(0, len(mylist)-1) as  
>>> a fix.
>>
>> This brings up an interesting proposal.
>> random.choice(seq) brings back a random element from a list, why not
>> add an optional second argument which is a flag to pop the element
>> instead of choosing?
>>
>> ie.
>>
> import random
> def choice(seq, pop=False):
>>
>> ... if not pop:
>> ... return seq[random.randrange(len(seq))]
>> ... else:
>> ... return seq.pop(random.randrange(len(seq)))
>> ...
>>
> x = [1, 2, 3]
> choice(x)
>>
>> 1
>>
> x
>>
>> [1, 2, 3]
>>
> choice(x, True)
>>
>> 1
>>
> x
>>
>> [2, 3]
>
> [The main reason I am answering your mail is because you may have  
> intended to
> post on c.l.py]
>
> Regarding your enhancement, I don't see any use cases that aren't  
> handled by
> random.sample() already.
>
> Regards,
> Peter

I can see a use case. Think of a bag datastructure. You push things  
into some container
and pop them out randomly. If random.choice was capable of 'pop' it  
would be
implemented implicitly.

random.sample, select elements from a list, but the original list  
remains intact. This would
not be the desired 'bag' behavior.


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http://and.rovir.us


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Re: New python.org site

[Steve Holden]

Luis M. González wrote:
> I wouldn't want to sound like I'm criticizing other people's work.
> To those who offered their time to create this site, which is quite an
> improvement over the old one, thank you!
> 
> However, I like the idea of a contest. Both for the site and for the
> logo.
> Perhaps something cool could come up from the new crop of
> Django/TurboGears fans our there...
> 
> For many people, these things may seem superfluos or not important at
> all, but good marketing and good design helps to create an image and an
> identity.
> 
I think you seriously underestimate the work it would take (and indeed 
has just taken and is currently taking) to reimplement the site.

"A competition" sounds like a wonderful idea, but suppose there were to 
be one, and a winner were to be declared, where do we go from there to 
get the winning design up on a server behind www.python.org?

regards
  Steve
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Re: Python and C

[Thomas Heller]

Terry Reedy wrote:
> "P Boy" <[EMAIL PROTECTED]> wrote in message 
> news:[EMAIL PROTECTED]
>>> Has anyone yet written a program to grab C struct declaration from the 
>>> .h
>>> to produce code like
>>>
>>> # Overlay configuration
>>> class OverlayStoreConfig(ctypes.Structure):
>>> _fields_ = [('FormatVersion',   ctypes.c_ulong),
>>> ('VolumeSize',  ctypes.c_longlong),
> etc
>> http://starship.python.net/crew/theller/ctypes/codegen.html says it can
>> be done. However, it requires MSVC 7.1 and I have not yet install it
>> since I already have MSVC (6,7,8) on my PC.
> 
> Or vc6.  Neither of which most people have, especially those not using Swig 
> because they don't do C.  Ok, we need program entirely in Python.  Possible 
> exercise for someone.
> 

Alan Green apparently has got it to work with the free vctoolkit:

http://cardboard.nu/blog/2005_07_14/ctypes_code_generator_for_chea.html


Thomas

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RE: What has become of the Python 2004 papers?

[Andrew Koenig]

> Try here:
> 
> http://us.pycon.org/zope/original/pycon/pastevents/dc2004
> 

I see summaries of the paper, but when I follow the link for the papers
themselves, it leads to the same dead end.



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Re: New python.org site

[Kay Schluehr]

Luis M. González wrote:
> I wouldn't want to sound like I'm criticizing other people's work.
> To those who offered their time to create this site, which is quite an
> improvement over the old one, thank you!
>
> However, I like the idea of a contest. Both for the site and for the
> logo.
> Perhaps something cool could come up from the new crop of
> Django/TurboGears fans our there...
>
> For many people, these things may seem superfluos or not important at
> all, but good marketing and good design helps to create an image and an
> identity.

I'm >0 on this. And besides the marketing or "evangelizing" aspect it
may happen that a new site is not only cool but also innovative? I'm
just not sure what will follow up? In a public competition among
architects the winner will finally be commissioned to create the
building and earn money for it. What could be the gift to an imaginary
winner of a Python site design competition? Sponsoring is a fine idea
but should banner advertisment be actually a part of the design
requirement?

Kay

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Re: What has become of the Python 2004 papers?

[A.M. Kuchling]

On Sat, 11 Mar 2006 12:00:26 -0600, 
[EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> I believe the plan is to move most/all the PyCon-related stuff to the
> pycon.org domain, though I'm not certain about that.

No, that's not the plan.  The PSF doesn't own the domain, and I want
the data to be available as static files, not via a web application.

--amk
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Re: Cheese Shop: some history for the new-comers

[A.M. Kuchling]

On Sat, 11 Mar 2006 16:50:26 +1100, 
richard <[EMAIL PROTECTED]> wrote:
> So I did what people always do in this situation, I asked Barry Warsaw to
> name. it. And he did, "Cheese Shop". I liked the name, so it was done. When
> the new pydotorg machines went live last year, so too did the name
> cheeseshop.python.org

Given the endless whiny complaints about the name, though, I think we
should just give up and go back to PyPI (pronounced 'Pippy').

--amk

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Re: API/C memory mananegemnt problem

[Alex Martelli]

<[EMAIL PROTECTED]> wrote:

> Sorry for responding to my own post.
> 
> I think I understand the original statement now.  What you are really
> saying is that there is a pool of Python float objects (which can, at
> different times, wrap different values) which can grow but never
> decrease in size.  So the memory held by this pool is dictated by the
> maximum number of floats that have ever been simultaneously active
> (accessible).
> 
> The same goes for integers.  All the more reason to avoid range(.) and
> use xrange(.).

Uh? The integers produced as you loop over xrange will be just immortal
as those that get into the list built by range, so why is int
immortality any reason to use one over the other?

If you know you're probably not going to loop over ALL the range or
xrange, sure, but that's relatively rare -- and, when it does occur,
xrange is seriously preferable:

helen:~ alex$ python -mtimeit 'for x in range(100): pass'
10 loops, best of 3: 15.9 usec per loop

helen:~ alex$ python -mtimeit 'for x in xrange(100): pass'
10 loops, best of 3: 12.2 usec per loop

helen:~ alex$ python -mtimeit 'for x in range(100): break'
10 loops, best of 3: 7.57 usec per loop

helen:~ alex$ python -mtimeit 'for x in xrange(100): break'
100 loops, best of 3: 1.5 usec per loop

The immediate break only halves the time requirements of the range-based
loop, but it slashes by 8 times those of the xrange-based one -- now
THAT is big enough to matter, as opposed to the 20% or so difference in
overhead when you're always looping all the way, which is unlikely to
make an important difference in overall application speed.


Alex
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Re: API/C memory mananegemnt problem

[Aahz]

In article <[EMAIL PROTECTED]>,
Alex Martelli <[EMAIL PROTECTED]> wrote:
><[EMAIL PROTECTED]> wrote:
>> 
>> I think I understand the original statement now.  What you are really
>> saying is that there is a pool of Python float objects (which can, at
>> different times, wrap different values) which can grow but never
>> decrease in size.  So the memory held by this pool is dictated by the
>> maximum number of floats that have ever been simultaneously active
>> (accessible).
>> 
>> The same goes for integers.  All the more reason to avoid range(.) and
>> use xrange(.).
>
>Uh? The integers produced as you loop over xrange will be just immortal
>as those that get into the list built by range, so why is int
>immortality any reason to use one over the other?

Because unless you save the ints produced by xrange(), you're reusing
slots in the free list as you go through the loop, whereas range() chews
up a gob of memory that will never get released even if you never
otherwise use all the ints it produces.
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is not worth knowing."  --Alan Perlis
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Re: New python.org site

[Bertrand Mansion]

On 3/11/06, Steve Holden <[EMAIL PROTECTED]> wrote:

> "A competition" sounds like a wonderful idea, but suppose there were to
> be one, and a winner were to be declared, where do we go from there to
> get the winning design up on a server behind www.python.org?

That's not the problem IMO.

Before launching any contest, it should be made clear what needs to be
done by contestants. This involves writing an organized chart of
existing (or not) content and detailed guidelines.

For the contest, contestants will get a copy of these guidelines:
- First, second, third navigation levels.
- Python history, positioning, etc.

If these guidelines are clear and respecting these guidelines becomes
a part of the final applications evaluation, then it will be easy to
adapt the winning results to the site. I have looked at
http://psf.pollenation.net, the current python.org svn, and it seems
python.org currently doesn't work with any database backend... It
seems to be just a plain ol' html site built upon YAML files. There
can't probably be an easier configuration.

BTW, this is a interesting read and could be used as a basis for the guidelines:


The big part is really deciding what is proposed and what goes where.


Bertrand
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Re: Why property works only for objects?

[Michal Kwiatkowski]

Alex Martelli napisał(a):
> First, let's forget legacy-style classes, existing only for backwards
> compatibility, and focus on new-style ones exclusively -- never use
> legacy classes if you can avoid that.

Ok, let's cover only new-style classes in our discussion.

I've read your comments and am on a way of reading your articles. Still,
with my current knowledge I'm trying to write pure python attributes
lookup function. I've failed for example given below:

class C(object):
__dict__ = {}

obj = C()
obj.a = 7
obj.__dict__ = {}
print object.__getattribute__(obj, '__dict__')
print object.__getattribute__(C, '__dict__')
print obj.a  # => 7 !!!

First print returns "{}" and the second returns

{'__dict__': {},
 '__module__': '__main__',
 '__weakref__': ,
 '__doc__': None}

Neither of them have "a" attribute. How come obj.a doesn't raise an
exception? Where obj.a is kept?

mk
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 o o o   than forgiveness for being right.
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Re: Python source cross reference doc generator?

[Colin J. Williams]

Harry Fuecks wrote:
> Hi All,
> 
> Wondering if a tool exists to generate "cross reference" documentation
> for Python code bases?
> 
> Particularly after something like phpxref -
> http://phpxref.sourceforge.net/ : written in Perl, scans a bunch of
> PHP scripts and generates HTML output that allows you to see all the
> classes / methods / functions / variables defined and (what I'm
> interested in) where they are referenced. Essentially something like
> API docs but with the addition of being able to see who's using a
> particular method
> 
> Is there anything like this for Python? Have done much looking without 
> success.
> 
> Many thanks.
epydoc and pydoc each provides an index.  If you are looking for info on 
where a name is defined or used, PyScripter is helpful.

Colin W.
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Re: Advice for creating a web app

[Olivier]

Hi there,


Jumping until blue a écrit :
> I have a number of files, mostly text files formatted using Markdown
> syntax but also pdfs and other types of files, that are stored in a
> folder hierarchy and I want to develop a web application where I can
> brows, view and search these files. The documents can be
> cross-linked.
> 
> Currently I use a basic CGI to view/format the markdown files but I
> don't know if I should continue to make my own system or if I should
> take advantage of some existing framework.
> 
> My requirements are:

...

You may be interested in pyblosxom (http://pyblosxom.sourceforge.net/).

It's filesystem based, allows different input formats (html, rest, plain 
text, I don't know about "Markdown syntax"), allows also to serve what 
they call static files (like your pdfs), and you can plug some search 
capacities (for instance, a wrap around grep).

I used to run it behind apache with cgi, but it should be possible to 
use it with a lightweight-no install web server.

HTH,

Olivier
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Re: New python.org site

[Kay Schluehr]

Bertrand Mansion wrote:
> On 3/11/06, Steve Holden <[EMAIL PROTECTED]> wrote:
>
> > "A competition" sounds like a wonderful idea, but suppose there were to
> > be one, and a winner were to be declared, where do we go from there to
> > get the winning design up on a server behind www.python.org?
>
> That's not the problem IMO.

Em, why not IYO? Because you will implement it however advanced the
design might be as part of your Python exercises?

Kay

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Help Create Good Data Model

[mwt]

Hi. I'm reworking a little app I wrote, in order to separate the data
from the UI. As a start, I wanted to create a iron-clad data recepticle
that will hold all the important values, and stand up to being queried
by various sources, perhaps concurrently. In all likelihood, the app
will never need anything that robust, but I want to learn to write it
anyway, as an exercise. So here is my code. It's really simple, and I'm
sure you can see my Java background. Are there any problems here?
Something I'm missing or screwing up? I welcome any and alll feedback,
especially if it includes the *why's.* Thanks!

#!/usr/bin/python
# author mwt
# Mar '06

import copy, threading

class FAHData(object):
"""The data model for the [EMAIL PROTECTED] monitor."""

def __init__(self):
self.data = {}#this dict will hold all data
self.mutex = threading.RLock()

def get_all_data(self):
"""Returns a COPY of entire data dict."""
#not sure deepcopy() is really necessary here
#but using it for now
#might cause some weird synchronization problems...
try:
self.mutex.acquire()
return copy.deepcopy(self.data)
finally:
self.mutex.release()

def get_data(self, key):
"""Returns a COPY of  data element."""
try:
self.mutex.acquire()
return copy.deepcopy(self.data[key])
finally:
self.mutex.release()

def set_value(self, key, value):
"""Sets value of  data element."""
try:
self.mutex.acquire()
self.data[key] = value
finally:
self.mutex.release()

def set_data(self, data):
"""Sets entire data dictionary."""
try:
self.mutex.acquire()
self.data = data
finally:
self.mutex.release()

def clear_data(self):
"""Clears entire data dictionary."""
try:
self.mutex.acquire()
self.data = {}
finally:
self.mutex.release()

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Re: New python.org site

[Michael Tobis]

I think a logo contest is a good idea, and I am already working on my
entry.

I could also imagine a stylesheet contest.

The issue is who does the judging and what are the criteria.

Steve, what you say is true. Possibly people who are experienced in
making a six page site for their aunt's catering business may not
understand how much the site implementation is constrained by the huge
amount of existing content, nor what an excellent effort the rework is,
nor what a good product was achieved.

I am trying to make the point that the silly logo cancels out a good
bit of the benefit of the site in appealing to the uncommitted. A brand
that people love is usually a part of a product that people love, and
there needs to be some correspondence.

A pink bunny is a fine brand for flashlight batteries, but not a good
one for motorcycles.

For a language which cannot avoid associations with a ten meter snake,
a pair of tadpoles just says "we don't really mean it, never mind". The
twistedmatrix logo and the pycon logo take advantage of the
associations. The tadpoles try to avoid them, and to make matters worse
pick up a vague and oddly disturbing religious affiliation in the
process. If we are serious about promoting the language, they really
have got to go.

The contest can specify the dimensions of the logo image to match those
of the one currently on the site. The amount of work required to
replace the existing logo with a more appropriate one would amount to
just changing one reference in a stylesheet.

Michael

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Re: Why property works only for objects?

[Alex Martelli]

Michal Kwiatkowski <[EMAIL PROTECTED]> wrote:

> class C(object):
> __dict__ = {}
> 
> obj = C()
> obj.a = 7
> obj.__dict__ = {}
> print object.__getattribute__(obj, '__dict__')
> print object.__getattribute__(C, '__dict__')
> print obj.a  # => 7 !!!
> 
> First print returns "{}" and the second returns
> 
> {'__dict__': {},
>  '__module__': '__main__',
>  '__weakref__': ,
>  '__doc__': None}
> 
> Neither of them have "a" attribute. How come obj.a doesn't raise an
> exception? Where obj.a is kept?

It's easier to trace if you use a unique value rather than 7 ...:

>>> class C(object):
...   __dict__ = {}
... 
>>> obj = C()
>>> obj.a = object()
>>> import gc
>>> gc.get_referrers(obj.a)
[{'a': }]

so, at this point, you know that obj.a is kept in a dictionary where
it's the only value.  That's the dictionary you would USUALLY be able to
get to as obj.__dict__, but...:

>>> obj.__dict__
{}

...the presence of '__dict__' as an entry in C is confusing the issue,
because that's what you get in this case as obj.__dict__.

C.__dict__ gives you a dictproxy, not a real dict, by the way:

>>> obj.__dict__ is C.__dict__['__dict__']
True

The funny thing is that builtins like var, which should know better,
also get fooled...:

>>> vars(obj)
{}
>>> vars(obj) is C.__dict__['__dict__']
True

...and so does the assignment to obj.__dict__...:

>>> obj.__dict__ = {}
>>> gc.get_referrers(obj.a)
[{'a': , '__dict__': {}}]

Now, both obj.a and obj.__dict__ are entries in a dictionary where
they're the only two entries -- exactly the dictionary that would
NORMALLY be obj.__dict__.

I think a fair case can be made that you've found a bug in Python here:
the existence of that __dict__ in C's class body is clearly causing
unintended anomalies.  Fortunately, getattr and friends don't in fact
get confused, but vars does, as does assignment to obj.__dict__...


Alex
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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[EleSSaR^]

robert si è profuso/a a scrivere su comp.lang.python tutte queste
elucubrazioni: 

> own deepcopy: thus, do you already know if the existing deepcopy has the 
> same problem as cPickle.dump ?(as the problem araises rarely, it is 
> difficult for me to test it out)

I don't know the exact specs of your object, and I don't know what
operations are you performing on that object, nor the way they're atomic.

It seems like you're trying to save periodically the state of such object
while it is being modified (a sort of backup?), and Python complains about
that. A self-implemented deepcopy might raise anomalies (i.e. your dumped
object may be partly a 'before' object and partly an 'after' object ) as
well. 

By the way, you could try employing locks from other threads to dump the
object as well... this would prevent additional locking.
 
> PS: how does ZODB work with this kind of problem? I thought is uses cPickle?

I have no idea about this.


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Re: "RuntimeError: dictionary changed size during iteration" ; Good atomic copy operations?

[EleSSaR^]

robert si è profuso/a a scrivere su comp.lang.python tutte queste
elucubrazioni: 

[cut]

P.S.
I'm very bad at threaded programming. Please verify any of my suggestions
^_^


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How to refer to the function object itself in the function per se?

[Sullivan WxPyQtKinter]

When debugging using 'print' statement, I usually want to print some
important values together with the function name as the context of the
values printed out. So my hope is that I could get the name of the
function.

Since every function object actually has a private __name__ attribute
that gives its name, but when I

print __name__

in a function, it usually print the public module-level __name__
attribute, ie, 'main', rather than the function level __name__. So how
could I refer to the function object per se, in the body of the
function itself?

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Re: Help Create Good Data Model

[fumanchu]

There's nothing really *broken* jumping out at me. The last three
methods (set_value, set_data, and clear_data) probably don't need a
mutex, since they will each have their own frame, and the operations
are atomic. If that makes no sense, Google for "Python GIL" ;). If you
just returned a value from the dict instead of using copy, the same
might be said for the get methods--it depends on whether you're storing
mutable objects in self.data or not.

When you're done with the exercise and want to persist those values
somewhere, give Dejavu a try: http://projects.amor.org/dejavu/


Robert Brewer
System Architect
Amor Ministries
[EMAIL PROTECTED]

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Re: Help Create Good Data Model

[Sybren Stuvel]

mwt enlightened us with:
> I'm reworking a little app I wrote, in order to separate the data
> from the UI.

Good idea.

> As a start, I wanted to create a iron-clad data recepticle that will
> hold all the important values, and stand up to being queried by
> various sources, perhaps concurrently.

Why do that yourself, if you can have SQLite databases? SQLite is even
capable of in-memory databases. No need to re-invent the wheel.

Sybren
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capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
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Re: New python.org site

[Bertrand Mansion]

On 11 Mar 2006 11:52:35 -0800, Kay Schluehr <[EMAIL PROTECTED]> wrote:

> Em, why not IYO? Because you will implement it however advanced the
> design might be as part of your Python exercises?

Look at the current code, there is nothing to implement. Most of the
work to be done is related to presentation and content organization.

Now, there are also new features we might want:

- documentation with user comments (like in PHP, Postgres, MySQL...)
- RSS feeds
- Efficient search engine (hyperestraier ?)
- Database backend and CMS

Those will certainly need code. Feel free to exercise your Python
skills on that, it would be more useful than your unconstructive
comments.


Bertrand Mansion
Mamasam
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Re: Cheese Shop: some history for the new-comers

[Tim Churches]

A.M. Kuchling wrote:
> On Sat, 11 Mar 2006 16:50:26 +1100, 
>   richard <[EMAIL PROTECTED]> wrote:
>> So I did what people always do in this situation, I asked Barry Warsaw to
>> name. it. And he did, "Cheese Shop". I liked the name, so it was done. When
>> the new pydotorg machines went live last year, so too did the name
>> cheeseshop.python.org
> 
> Given the endless whiny complaints about the name,

I was just hoping that honour would be bestowed upon me for suggesting a
brilliant alternative name, but I sense it is not to be...oh well
(whistles tune to himself).

> though, I think we
> should just give up and go back to PyPI (pronounced 'Pippy').

Perusable Index of Packages for PYthon -> PIPPY (or PipPy if CamelCase
is preferred, or pippy...).

PyPi is doomed to be mispronounced pie-pie.

Anyway, thanks to Richard Jones for all his work on PyPI/Cheese Shop,
whining about the name notwithstanding.

Tim C

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Re: How to refer to the function object itself in the function per se?

[Duncan Booth]

Sullivan WxPyQtKinter wrote:
> So how
> could I refer to the function object per se, in the body of the
> function itself?
> 
> 
I don't believe you can easily get at the function object, but you can get 
at the code object which also has a name (which will be the same as the 
function's name unless you've been doing strange things):

>>> import inspect
>>> def f():
print inspect.currentframe().f_code.co_name


>>> f()
f

For convenience you might want to put this inside a function:

>>> def myname():
f = inspect.currentframe().f_back
return f.f_code.co_name

>>> def f():
print myname()


>>> f()
f

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