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Python

__Main__

what does this do

def main():
    pass

if __name__ == "__main__":
    main()

[MOD: added ```python formating -cf]

2 Answers

Steven Parker
Steven Parker
229,921 Points

"Pass" does nothing, so currently the "main" function does not do anything.

Without Markdown formatting, the original syntax is lost, but assuming you meant to test "__name__", that determines if the file is being run by itself instead of being included by another program.

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,423 Points

Good question! This is a common python idiom to detect if a module is imported or being executed directly.

When a python module is imported into another module, its __name__ attribute is set to be the same as the module name. When a python module is executed, the top level module attribute __name__ is changed to be "__main__". This way a module can tell the difference between if it is being imported or executed.

The python idiom

if __name__ == "__main__":
     main()

says, "if my __name__ attribute has been changed to the string "__main__", then execute the function main(). The "pass" would be replaced with the code to be executed.

Post back if you have more questions. Good luck!!