Re: Parsing a commandline from within Python

[Andreas Huesgen]

>> Is there any buildin function which mimics the behavior of the
>> standard commandline parser (generating a list of strings
>> "foo bar" and "some text" from the commandline
>> <"foo bar" "some text">)?
> 
> Try the shlex module::
> 
>  >>> import shlex
>  >>> shlex.split('"foo bar" "some text"')
>  ['foo bar', 'some text']
> 

Thanks, that is exactly what i need.


Andreas Huesgen
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Parsing a commandline from within Python

[andreas . huesgen]

Hello,

I am writing a commandline tool in Python which is often feed with lots of 
commandline arguments. In practice, the commandline already reached a critical 
length which is to long for Windows (some versions of Windows only support 
commandlines of up to 2047 characters). To work around this problem, we thought 
up the idea of bypassing the commandline into a file and then letting Python 
parse the content of the file the same way, the arguments in sys.argv are 
parsed.

Is there any buildin function which mimics the behavior of the standard 
commandline parser (generating a list of strings "foo bar" and "some text" from 
the commandline <"foo bar" "some text">)?

If not, do you have any other ideas how to handle this problem (increasing 
commandline length, xml files might be a way)?


Regards,

Andreas Huesgen

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Find out the name of a variable passed as an argument

[Andreas Huesgen]

Hello everybody,

is there a way to receive the name of an object passed to a function 
from within the function.

something like

def foo(param):
print theNameOfTheVariablePassedToParam

var1 = "hello"
var2 = "world"

 >>> foo(var1)
var1

 >>> foo(var2)
var2

thanks in advance,

greets

Andreas Huesgen

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Re: python reference counting and exceptions

[Andreas Huesgen]

Delaney, Timothy (Tim) wrote:
> RIIA - Resource Initialisation is Acquisition
> 
> Python is adding an RIIA mechanism in 2.5 - look at the "with"
> statement.
> 

Ah, thanks, thats exactly what I was looking for.


Gabriel Genellina wrote:
> Yes: the try/finally construct, which is *not* the same as a try/except. The 
> finally clause is always executed, whether or not an exception is raised.

Yes, of course it must be the try finally construct and not try/except. 
Shame on me ;)

Andreas Huesgen
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python reference counting and exceptions

[Andreas Huesgen]

Hello,

I have a question refering python's reference counting/garbage 
collection in combination with thrown exceptions.

I'm very new to this mailinglist, so I hope, that this question has not 
been asked and answered before.

In c++, it is possible to write a locking system similar to the one below:


void myFunction()
{
# create a resource lock. Locks some resource
ResourceLock myLock;

# the following line may throw an exception
doStuff();
}


myLock is a stack variable which is destroyed as soon as the function is 
left (either by returning or because of an uncatched exception). As 
myLock is destroyed, the destructor will automatically unlock the resource.

The following python code has the same effect (at least on my system and 
my python implementation).


class MyLock(object):
 def __init__(self):
 print "MyLock.__init__"

 def __del__(self):
 print "MyLock.__del__"

def myFunction():
 print "prelock"
 lock = MyLock()
 print "postlock"

print "prefun"
try:
 myFunction()
except Exception, e:
 print str(e)
print "postfun"

output is:
prefun
prelock
MyLock.__init__
postlock
MyLock.__del__
postfun
MyLock.__init__
MyLock.__del__


However, when myFunction raises an exception, lock is not destroyed as 
soon as the function is exited but only at the end of the script


My question is: is there some reliable way to mimic the c++ code snipped 
above in python without adding a try-except-unlock-rethrow block around 
every peace of code that locks some resources.


Greets,

Andreas Huesgen
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