if name 3d 3d 27 main 27

1if __name__ == "__main__":

1# If the python interpreter is running that module (the source file)
2# as the main program, it sets the special __name__ variable to have
3# a value “__main__”. If this file is being imported from another 
4# module, __name__ will be set to the module’s name.
5if __name__=='__main__':
6  # do something

1# It's as if the interpreter inserts this at the top
2# of your module when run as the main program.
3__name__ = "__main__" 

1# Suppose this is foo.py.
2
3print("before import")
4import math
5
6print("before functionA")
7def functionA():
8    print("Function A")
9
10print("before functionB")
11def functionB():
12    print("Function B {}".format(math.sqrt(100)))
13
14print("before __name__ guard")
15if __name__ == '__main__':
16    functionA()
17    functionB()
18print("after __name__ guard")

1python foo.py

1if __name__ == "__main__": main()