Python Main Guard

In Python, the construct if __name__ == "__main__": is often used to allow a script to be run either as the main program or imported as a module into another script.

When a Python script is executed, the special variable __name__ is set to "__main__" if the script is being run directly. If the script is imported as a module into another script, __name__ is set to the name of the module.

Therefore, if __name__ == "__main__": is a common idiom to specify code that should only be executed when the script is run directly, and not when it’s imported as a module. This is often used to define entry points or to execute specific setup code.

For example:

# my_script.py

def my_function():
    print("This is my function.")

if __name__ == "__main__":
    # This code block will only be executed if the script is run directly
    print("This script is being run directly.")
    my_function()

If you run my_script.py directly, you will see the output:

This script is being run directly.
This is my function.

But if you import my_script.py into another script, the if __name__ == "__main__": block will not be executed, and only the function definitions will be imported.