Newbie questions for Python usage
Hello, I am fairly new to Python and after exploring the language some I have some questions: I understand HOW to use the lambda operator, but WHY would you want to use it? Can anyone please give an example of WHY you would need it as opposed to just declaring a function either in the local scope, or outside? I would like to be able to declare as a member attribute a file object, however because there is no declaration of variable types like there is in C++, there doesn’t seem to be a way to do this without first making a fobj = open(…) call. Is this true? Now for an os import question for Windows. I wish to automate the builds of VS.NET 2005 and I can do so by executing the os.system(...) command however I cannot see how to execute the vcvars32.cmd first to set environment variables and then execute the actual command-line for the build itself. Thanks for the help all! Caolan-- http://mail.python.org/mailman/listinfo/python-list
RE: Newbie questions for Python usage
Title: Re: Newbie questions for Python usage
Thanks
Fred.
> just assign to the attribute and be done
with> it. if you want to use a placeholder value, use
None:
I thought I had tried that already but got an error.
I'll try it again, and as for the 2nd one, I was hoping to avoid the usage of
.cmd or .bat files altogether. Thanks!
-Caolan O'Domhnaill
From:
[EMAIL PROTECTED] on behalf of Fredrik
LundhSent: Tue 8/22/2006 4:08 PMTo:
python-list@python.orgSubject: Re: Newbie questions for Python
usage
Caolan wrote:> 1. I understand HOW
to use the lambda operator, but WHY would
you> want to use it? Can anyone
please give an example of WHY you
would> need it as opposed to just
declaring a function either in the>
local scope, or outside?you don't *need* it,
because callback = lambda arg:
_expression_is, for most practical purposes, the same thing
as def
callback(arg): return
_expression_(the only difference is that the __name__ attribute for the
functionobjects will differ; all lambdas are named "", while
objectscreated by "def" have the original name.)however, in some
cases, it's may be convenient to use the lambda form,for stylistic
reasons.> 2. I would like to be able to declare as
a member attribute a file> object,
however because there is no declaration of variable
types> like there is in C++, there
doesn’t seem to be a way to do this>
without first making a fobj = open(…) call. Is this true?not sure what
you mean, really -- attributes are not typed, and there'sno way to "declare"
them. just assign to the attribute and be done withit. if you
want to use a placeholder value, use None: class
foo: def
__init__(self):
self.file = None # not opened
yet def open(self,
name):
self.file = open(name)or class
foo: file = None # shared
placeholder def
__init__(self):
pass def open(self,
name):
self.file = open(name)> Now for an os import question for Windows. I
wish to automate the> builds of VS.NET 2005 and I can do so by executing
the os.system(...)> command however I cannot see how to execute the
vcvars32.cmd first to> set environment variables and then execute the
actual command-line for> the build itself.there's no easy way to
do that: environment variables set by a sub-process isn't available to the
main process.the easiest way to do this might be to simply generate a
short temporaryBAT-file for each command, and do os.system() on that
file: f = open("temp.bat",
"w") f.write("@call
vcvars32.bat\n") f.write("cl
...\n") f.close()
os.system(f.name)
os.remove(f.name)--http://mail.python.org/mailman/listinfo/python-list
--
http://mail.python.org/mailman/listinfo/python-list
RE: in-memory-only file object from string
Title: in-memory-only file object from string The mmap module should do what you are looking for. It allows you to store data in memory (hence the name memory map) and treat it as both a string and a file. From: [EMAIL PROTECTED] on behalf of bobrikSent: Wed 8/23/2006 2:56 PMTo: python-list@python.orgSubject: in-memory-only file object from string Hello,how to create a file object whose contents I initialize from a stringand which is purely in memory?I can make a workaround like this:filecontents = "Very interesting stuff ... "file = os.tmpfile ()file.write (filecontents)file.seek (0)procedure (fileobject = file)but this creates a file on harddisk. Instead I would like to usesomething like:filecontents = "Very interesting stuff ... "file = stringfile (filecontents)procedure (fileobject = file)Is this possible somehow? I appreciate any help.--http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
RE: Best Editor
Title: Re: Best Editor I like ActiveState's KOMODO editor. It is multilanguage compiler editor. Its not free but it is inexpensive for what it does, IMO. I believe they have a 30day free trial and a version for both platforms you mentioned. -Caolan. From: [EMAIL PROTECTED] on behalf of Michiel SikmaSent: Thu 8/24/2006 4:41 AMTo: JAG CHANCc: python-list@python.orgSubject: Re: Best Editor I personally use Eclipse with PyDev. It is a cross-platform solution because Eclipse is made with Java.http://www.eclipse.org/http://pydev.sourceforge.net/MichielOp 24-aug-2006, om 13:29 heeft JAG CHAN het volgende geschreven:> Friends, I am trying to learn Python.> It will be of great help to me if you let me know which one would > be best> editor for learning Python.> Plese note that I would like to have multiplatform editor which > will be> useful for both LInux and Windows XP.> Thanks.> --> http://mail.python.org/mailman/listinfo/python-list--http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
How to include and use a .NET DLL and namespace.
Hello, I am in need of importing in a .NET namespace from a built DLL. How do I get Python to pickup and recognise the namespace and classes in the DLL? Thanks, Caolan O'Domhnaill-- http://mail.python.org/mailman/listinfo/python-list
Newbie question involving buffered input
I am executing the code below on a Windows XP system and if I enter > 2 characters it buffers the input and the call to sys.stdin.flush does not flush the input, it remains buffered. What am I doing wrong here? Thanks, Caolan try: gooberselectX = sys.stdin.read(2) except IOError, e: print 'error reading from stdin device' except KeyboardInterrupt, e: print 'you cannot break. please use the \'q\' key to exit' else: try: sys.stdin.flush() except IOError, e: print 'error flushing buffered input'-- http://mail.python.org/mailman/listinfo/python-list
RE: Newbie question involving buffered input
Title: Re: Newbie question involving buffered input That makes sense I suppose - why is there a stdin.flush() method then? From: [EMAIL PROTECTED] on behalf of Jean-Paul CalderoneSent: Fri 9/1/2006 9:53 AMTo: python-list@python.orgSubject: Re: Newbie question involving buffered input On Fri, 1 Sep 2006 09:31:11 -0700, Caolan <[EMAIL PROTECTED]> wrote:>I am executing the code below on a Windows XP system and if I enter > 2 characters it buffers the input and the call to sys.stdin.flush does not flush the input, it remains buffered.You cannot flush input. The flush method only relates to output. The*other* side of the file has to flush *its* output in order for you tosee it as input.On Linux, the termios module provides a way to tell the system not to doany buffering on a file descriptor. pywin32 may expose equivalentfunctionality for Windows.Jean-Paul--http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
