What does if __name__ == “__main__”: do?

If you have started working with python, then in python files you must have seen the following code as the last lines

if __name__ == "__main__":
    main()

Being a NodeJS/Angular developer, I was confused about this line. So here is the explanation

1. import a action actually runs all that can be ran in a.py, meaning each line in a.py
2. Because of point 1, you may not want everything to be run in a.py when importing it
3. To solve the problem in point 2, python allows you to put a condition check
4. __name__ is an implicit variable in all .py modules:

• when a.py is imported, the value of __name__ of a.py module is set to its file name "a"
• when a.py is run directly using "python a.py", the value of __name__ is set to a string __main__

5. Based on the mechanism how python sets the variable __name__ for each module, do you know how to achieve point 3? The answer is fairly easy, right? Put a if condition: if __name__ == "__main__": // do A

• then python a.py will run the part // do A
• and import a will skip the part // do A

6. You can even put if __name__ == "a" depending on your functional need.

Reference

https://stackoverflow.com/questions/419163/what-does-if-name-main-do#:~:text=In%20short%2C%20use%20this%20'%20if,when%20the%20module%20is%20imported.&text=Put%20simply%2C%20__name__,run%20as%20an%20imported%20module.