[Tutor] The IF statement
kent37 at tds.net
Thu Sep 6 00:03:36 CEST 2007
Toby Holland wrote:
> Hi gang,
> Just doing what I can to understand as I study
> I have been reading about testing modules this is the statement that I
> have been given
> if __name__ == "__main__":
> I understand that all modules have a built in attribute __name__, but
> what does the __main__ have to do with this attribute. Is it saying
> that __name__ is the same as __main__?
Yes. Note that __name__ is a variable and "__main__" is a string. So
this says that the value of the variable __name__ is the string "__main__".
> I know that if the module is imported then __name__is the moules file
It is the module name which is not quite the same as the file name.
__file__ has the file name.
> but is this just for the script that your writing while using that
> module or is it just to show that the module was imported?
It is a way to tell if the module was imported or run directly as a script.
> correct me if I'm wrong please, the modules file name is __main__ when
> its being used as a stand alone program?
The modules name, not the file name; otherwise yes.
> If this is the case the difference is whether or not the module is a
> program by itself or intigrated with a script that is what determines
> its name (i.e. __name__ and __main__)
It is handy to be able to write a module so it can be used by being
imported into another module, or by being run on its own. When run on
its own it might provide a simple command line interface or run unit
tests or whatever the developer finds useful. When imported as a library
for another module then this behaviour is not wanted so it is hidden by the
if __name__ == '__main__':
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