> What are pipes? The docs barely touched this subject, it assumed you already
> knew what they are... From context I am gathering that it is a connection to
> the kernel? (maybe?) How can I utilize this?
Pipes are a feature of the operating system, not of Python; and then,
mostly in POSIX operating systems. They are often used to connect the
output of one process to the input of another. For example on MS-DOG,
it is common to run `type autoexec.bat | more' to pause listing the
file after every screenful, the "|" is the pipe character. Refer to a
lot of shell scripting or UNIX system programming books for different
ways to utilize this fairly powerful construct.
> 1 more quickie:
> >if __name__ == '__main__':
> > main()
>
> what is the pourpose if the above code? It runs the sub main() (duh :) but,
> why not just main() wihtout the if? what is the conditional testing for?
> and what are the variables __main__ and __name__? i dont believe they are
> defined in the program, so just what are they? and, what does putting "__"
> around a variable actually DO besides look cool ?
This is explained in the Python FAQ 4.10 "How do I find out whether I
am running as a script?" Each module has a variable called
"__name__". If variable contains the name "__main__", then the module
is what was called from the command line (the "script"), instead of
imported from another module.
$ cat foo.py
if __name__ == '__main__':
print 'script'
else:
print 'imported'
$ python foo.py
script
$ python
>>> import foo
imported
>>>
Most often it is used to test a module meant to be imported, so only if
you execute it directly, it runs the testing code.
-Arcege
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