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Python: name

The predefined global variable __name__ is a string whose value corresponds to the module where it is evaluated.

If the source code that contains __name__ is executed as a script (rather than imported), the value of __name__ is __main__.

This behavior can be demonstrated with the following simple Python source file (tq84.py):

if __name__ == '__main__':
   print('This source is run as a script')
else:
   print('This source was imported, __main__ = {}'.format(__name__))

This script prints This source is run as a script if it is executed from the command line like so:

$ python tq84.py

Conversely, it prints This source was imported, __main__ = tq84 if it is imported from another script like so:

import tq84

Python: __name__