“if __name__ == __main__:”有什么作用

“if __name__ == __main__:”的作用：指定主方法函数。在脚本执行时开启main函数，但是在其他文件import调用时不会执行。

一个python的文件有两种使用的方法，第一是直接作为脚本执行，第二是在其他文件的python脚本中被import即调用（模块重用）执行。因此if name == 'main':的作用就是控制这两种情况执行代码的过程，在if name == 'main':下的代码只有在第一种情况下（即文件作为脚本直接执行）才会被执行，而import到其他脚本中是不会被执行的。

例子：

# 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")

# 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")

当运行python one.py，输出:

top-level in one.py
one.py is being run directly

当运行python two.py,输出:

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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