Feature Requests item #1637365, was opened at 2007-01-17 05:11
Message generated for change (Comment added) made by gbrandl
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Category: Documentation
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Gabriel Genellina (gagenellina)
Assigned to: Nobody/Anonymous (nobody)
Summary: if __name__=='__main__' missing in tutorial
Initial Comment:
I could not find any reference to the big idiom:
if __name__=="__main__":
xxx()
inside the Python tutorial. Of course it is documented in the Library Reference
and the Reference Manual, but such an important idiom should be on the Tutorial
for beginners to see.
I can't provide a patch, and English is not my native language, but I think a
short text like the following would suffice (in section More on Modules, before
the paragraph "Modules can import other modules..."):
Sometimes it is convenient to invoke a module as it were a script, either for
testing purposes, or to provide a convenient user interfase to the functions
contained in the module. But you don't want to run such code when the module is
imported into another program, only when it's used as a standalone script. The
way of differentiate both cases is checking the \code{__name__} attribute: as
seen on the previous section, it usually holds the module name, but when the
module is invoked directly, it's always \samp{__main__} regardless of the
script name.
Add this at the end of \file{fibo.py}:
\begin{verbatim}
if __name__=="__main__":
import sys
fib(int(sys.argv[1]))
\end{verbatim}
and then you can execute it using:
\begin{verbatim}
python fibo.py 50
1 1 2 3 5 8 13 21 34
\end{verbatim}
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>Comment By: Georg Brandl (gbrandl)
Date: 2007-07-12 09:38
Message:
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Originator: NO
Added a section about this in rev. 56306, 56307 (2.5).
----------------------------------------------------------------------
Comment By: Bj�rn Lindqvist (sonderblade)
Date: 2007-07-10 11:10
Message:
Logged In: YES
user_id=51702
Originator: NO
I just ran into this "problem" today, when teaching someone python. It is
definitely a glaring omission and needs to be fixed.
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