python if __name__ == "__main__"

Before understanding of this is:

__name__ == IF "__main__": 
    # this time you can execute the program

 

method one: 

This is in your own eye, you think you are __main__

For example

print('hello world!')
print('__name__value:',__name__)

def main():
    print('This message is from main function')

if __name__ == "__main__":
    main()

　　Code is executed, the output

hello world!
__name__value: __main__
This message is from main function

　　We can get analysis: At this time __name__ == "__main__"

Therefore, the output of the second sentence __main__

In if __name__ == "__main__": this sentence, apparently set up, we direct the implementation of main (content of the function), the output This message is from main function

 

And back to a situation

此为print_func.py

print('hello world!')
print('__name__value:',__name__)

def main():
    print('This message is from main function')

if __name__ == "__main__":
    main()

　　Another python file print_module.py

import print_func
print("Done!")

　　This time output Shane?

We analyze: first in print_module.py, that is in the eyes of others, __ name__ == "print_func", no longer perform print_func.py in if __name__ == "__main__": statement

Then the output

hello world!
__name__value: print_func
Done!

　　

to sum up

Run their own programs, __ name__ is the __main__

When the program is invoked as a script to run other people, it __name__ for their module name, print_func here are imported into print_module as the script is running, the print_func of __name__ That becomes its own module name.