python supports several forms of starting a script. The usual one is python foo.py; in that case, foo.py would be simply executed. However, you can also do python -m foo. If foo is not a package, then foo.py is found in sys.path and executed. If it is, then Python executes foo/__init__.py, and foo/__main__.py after that. Note, that __name__ is equal to foo during __init__.py execution, but it's __main__ during __main__.py execution. You also can do python dir/ or even python dir.zip. In that case, dir/__main__.py is looked for and executed if found. $ ls foo __init__.py __main__.py $ cat foo/__init__.py print(__name__) $ cat foo/__main__.py print(__name__) $ python -m foo foo __main__ $ python foo/ __main__ $ python foo/__init__.py __main__