PythonNote019--Python中main

介绍​​-if __name__ == '__main__'​​​的用法，Talk is cheap,Show me the code.
两个脚本：

file one.py

# file one.py
def 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.py

# file two.py
import one

print("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")

run one.py

top-level in one.py
one.py is

这里的逻辑很正常，调用脚本时，先输出print语句，然后​​__name__​​​是其本身，所以输出​​one.py is being run directly​​

run two.py

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

逻辑如下：

1. import one时，print语句正常输出
2. 当前模块名为two，所以​​__name__​​​不是​​one​​,输出one.py is being imported into another module
3. 此时import one结束，two中的print正常输出​​top-level in two.py​​
4. 调用one模块中的func函数输出​​func() in one.py​​
5. 最后判断模块名，当前模块名为​​two​​​，所以输出​​two.py is being run directly​​

Summary

简单总结下，如果是把脚本作为模块调用​​import​​​，则​​if __name__ == "__main__":​​​不运行，但是如果作为脚本直接运行，那么执行​​if __name__ == "__main__":​​后面的程序。

Ref

​​[1] https://www.zhihu.com/question/49136398/answer/114437881​​​ [2] ​​http://blog.konghy.cn/2017/04/24/python-entry-program/​​

                                     2018-03-25 于杭州