What does 'if __name__ == __main__:' do?

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Release: 2020-09-18 09:24:01
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The role of "if __name__ == __main__:": specifies the main method function. The main function is started when the script is executed, but will not be executed when other files are imported.

What does 'if __name__ == __main__:' do?

There are two ways to use a python file. The first is to execute it directly as a script, and the second is to be imported in the python script of other files. Call (module reuse) execution. Therefore, the function of if name == 'main': is to control the process of executing the code in these two situations. The code under if name == 'main': can only be executed in the first situation (that is, the file is directly executed as a script). will be executed, but importing it into other scripts will not be executed.

Example:

# file one.pydef func():
    print("func() in one.py")
print("top-level in one.py")if __name__ == "__main__":
    print("one.py is being run directly")else:
    print("one.py is being imported into another module")
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# file two.pyimport one        # start executing one.pyprint("top-level in two.py")
one.func()if __name__ == "__main__":
    print("two.py is being run directly")else:
    print("two.py is being imported into another module")
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When running python one.py, the output is:

top-level in one.py
one.py is being run directly
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When running python two.py, the output is:

top-level in one.py
one.py is being imported into another module
top-level in one.pyfunc() in one.py
two.py is being run directly
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