What is __name__ and __main__ in python?

As a Python enthusiast, you’re likely digging into others’ code, seeking to learn and understand more. This self-driven exploration is indeed a fantastic way to enhance your skills. However, it’s natural to come across a few puzzling aspects, like __main__ or __name__, leaving you a bit befuddled. These are powerful constructs within Python that control how scripts and modules execute. They might seem a bit obscure initially, but understanding them can unlock a new level of Python proficiency.

__name__ and __main__ are built-in variables in Python that control the execution of modules and scripts.

__name__ is a built-in variable in Python, which is automatically set to the name of the module. If the module is being run directly (like when you run the script from the command line), its __name__ is set to __main__. However, if the module is being imported into another script or module, __name__ is set to the name of that module (which is the name of the .py file).

Here’s a small code example to illustrate:

# module1.py
def foo():
    print("Hello, I'm in module1")

if __name__ == '__main__':
    print("module1 is being run directly.")
    print("module1 is being imported into another module.")

If you run module1.py from the command line, you will see the message “module1 is being run directly.” However, if you import module1 into another script, you will see “module1 is being imported into another module.”

# module2.py
import module1


If you run module2.py from the command line, you will see “module1 is being imported into another module.”

The if __name__ == "__main__": idiom is used to ensure that certain parts of code are only run when the module is invoked directly, not when it is imported as a module. This can be useful for testing parts of your code, or when you want your module to be usable by other scripts, but also want it to be executable on its own.

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