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Understanding if __name__ == '__main__' in Python

This is one of the most confusing Python lines for beginners — but don't worry, we’ll break it down with real examples and make it crystal clear!

🔹What does if __name__ == "__main__" mean in Python?

Imagine you're writing a Python file — maybe a fun game or a simple calculator. Now ask yourself: should this file run some code only when it's opened directly? Or stay quiet if someone else imports it into their own project?

That’s exactly what if __name__ == "__main__" does! It's Python’s way of saying:
“Run this part only when the file is executed directly — not when it’s imported.”

This line checks a built-in variable called __name__. If you're running the file by double-clicking it or using python filename.py, then __name__ becomes "__main__". But if someone imports your file into another Python script, __name__ becomes the name of your file instead.

🔹So why should you care?

This small line is super useful when:

• You're writing utility functions that others might import.
• You want to test your code with print statements or small examples.
• You’re building Python scripts and want better control of when things happen.

Let’s understand with an example

# file: greet.py

def say_hello():
    print("Hello, world!")

if __name__ == "__main__":
    say_hello()

If you run greet.py directly, it will print Hello, world!.
But if you import greet into another file like this:

# file: app.py

import greet

Nothing will happen! Why? Because the code inside if __name__ == "__main__" block is ignored when the file is imported.
This helps keep your code clean and avoids running unwanted code when using modules.

Common Mistakes (Don’t fall for these traps!)

• Using = instead of ==: if __name__ = "__main__" is a syntax error. Always use == for comparison.
• Indentation Errors: The code inside the if block must be properly indented.
• Expecting code to run when imported: Remember, code inside if __name__ == "__main__" won't run when the file is imported.
• Forgetting the underscores: Don’t type if name == "main" — it must be __name__ and "__main__".

Wrap Up: You’ve Got This!

So now you know what if __name__ == "__main__" means in Python! It’s not as scary as it looked, right? Think of it as a way to tell Python: “Only run this part when I’m executing the file directly.”

This little line becomes really powerful when your projects grow or when you're sharing your code with others. Keep practicing, and you'll soon start using it like a pro without even thinking!

If you’re still unsure or got stuck somewhere — don’t worry. Scroll up, re-read slowly, and try it out in a small Python file. You’ll get the hang of it!

Hope this cleared your doubt!

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More coming soon — stay tuned and keep learning with Kiddo!