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if __name__ == "__main__"

The if __name__ == "__main__" construct in Python is used to execute a specific block of code only if the script is run directly. It helps in distinguishing whether the Python script is being run as the main program or being imported as a module in another script.

Purpose​

The primary purpose of using if __name__ == "__main__" is two-fold:

  1. Preventing Unintended Execution: When a Python script is imported as a module into another script, it may contain executable code outside of function definitions. Placing such code within the if __name__ == "__main__" block ensures that it will only execute when the script is run directly, preventing unintended execution when imported as a module.
  2. Providing a Main Entry Point: By placing the main functionality of a script within the if __name__ == "__main__" block, it explicitly indicates the entry point for execution. This improves code readability and helps other developers understand which part of the script is meant to be executed independently.

Example​

Consider the following example script connections.py:

import time

def connect():
    """Simulate connecting to the internet."""
    print("Connecting to internet...")
    time.sleep(1)
    print("Connected!")

if __name__ == "__main__":
    connect()

In this script, the connect() function is defined, and it is called within the if __name__ == "__main__" block. This ensures that connect() will only execute when connections.py is run directly.

Running the Script​

To run the script directly, execute the following command in the terminal:

python connections.py

This will execute the connect() function and simulate connecting to the internet.

Conclusion​

Using if __name__ == "__main__" is a good practice in Python scripting as it provides clarity on the intended execution flow of the script. By incorporating this construct, developers can ensure that their scripts behave as expected when run directly or imported as modules into other scripts.