python：如何判断文件是作为导入还是主脚本执行的？

Question

I'm writing a python file mylib.py

I'd like mylib.py to do something based on sys.argv if it's being executed as a script. But if it's imported from some other script, I don't want it to do that.

How can I tell if my python file is being imported or it's a main script?

(I've seen how to do this before, but I forgot.)

Answer 1

if __name__ == '__main__':
    # this was run as a main script

Here is the documentation on __main__ .

Usually this code is placed at the bottom of a module, and one common way to keep your code clean is to create a main() function that does all of the work, and only call that function inside of the conditional.

Answer 2

if __name__ == '__main__':
    # goes here only when module is being executed directly

Packages also can contain __main__ module, which is executed when you do python -m foo (or execute zipfile containing the package).

Answer 3

By using (placing the statements you want to be executed only when the module is running as main , not imported)

 if __name__ == "__main__":
        # this was run as a main script

Generally different statements have has to be placed in this ' if ' block like , module specific doctest call or print statements.The thing is by default (when running as main) the ' __name__ ' variable is set to " __main__ ", and otherwise (if imported ) the __name__ variable 'll get a different value, most probably the name of the module.