What is __name__ == "__main__" in Python?

If you are a Python beginner, you often see if __name__ == '__main__' and get confused about what it does. You are not alone. Most of my students at #PythonToProject Bootcamp struggle with this as well.

The if __name__ == '__main__': ensures that the snippet under it gets executed only when the file is run directly.

Running Python module

# app.py

print ("app.py __name__=", __name__)

if __name__ == '__main__':
    print ("inside main check block")

When you run this code python app.py you will get the following output

app.py __name__=__main__
inside main check block

Importing Python module

Whereas if you import app into another module

# temp.py
import app

print ("temp.py __name__=", __name__)

The output will be

app.py __name__=app
temp.py __name__=__main__