__main__.py 是什么? [英] What is __main__.py?

问题描述

__main__.py 文件是做什么用的，我应该放入什么样的代码，什么时候应该有一个?

What is the __main__.py file for, what sort of code should I put into it, and when should I have one?

推荐答案

通常，Python 程序是通过在命令行上命名 .py 文件来运行的:

Often, a Python program is run by naming a .py file on the command line:

$ python my_program.py

您还可以创建一个充满代码的目录或压缩文件，并包含一个 __main__.py.然后你可以在命令行上简单地命名目录或zipfile，它会自动执行__main__.py:

You can also create a directory or zipfile full of code, and include a __main__.py. Then you can simply name the directory or zipfile on the command line, and it executes the __main__.py automatically:

$ python my_program_dir
$ python my_program.zip
# Or, if the program is accessible as a module
$ python -m my_program

您必须自己决定您的应用程序是否可以从这样执行中受益.

You'll have to decide for yourself whether your application could benefit from being executed like this.

请注意，__main__ module 通常不是来自 __main__.py 文件.它可以，但通常不会.当您运行像 python my_program.py 这样的脚本时，该脚本将作为 __main__ 模块而不是 my_program 模块运行.对于以 python -m my_module 或其他几种方式运行的模块，也会发生这种情况.

Note that a __main__ module usually doesn't come from a __main__.py file. It can, but it usually doesn't. When you run a script like python my_program.py, the script will run as the __main__ module instead of the my_program module. This also happens for modules run as python -m my_module, or in several other ways.

如果您在错误消息中看到名称 __main__，这并不一定意味着您应该查找 __main__.py 文件.

If you saw the name __main__ in an error message, that doesn't necessarily mean you should be looking for a __main__.py file.

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