What is the purpose of the main function in programming?

[LCSphysicist]

TL;DR Summary

I was learning somethings about Python, but there is a function i didn't get what is your propose.

Is the main function really a function, or it is just the name we give to functions like "def Anyfunction: "? I searched about this "main function" and it always appears with the def command. So i am not sure what is the difference between both, if there is.

 

[jedishrfu]

It’s best explained here:

https://realpython.com/python-main-function/

Basically, it’s a convention for python scripts to define a main() function Where your application actually begins.

They use the construct:

def main():
    print("Hello World!")

if __name__ == "__main__":
    main()

what happens is the python interpreter reads your script in and then the first thing it does is evaluate the if __name__ statement which will return true and then execute the main() function.

Why use this convention?

My best guess is it models C programming and it allows you to either directly execute your script or import it into another script that may need some of your functions.

When used as an imported script the if __name__ will evaluate to false and the main() won’t be executed.

 

[anorlunda]

When you start your program, how does the system know which statement in your program to execute first? The main function is a convention to indicate where to start.

Also, following C and Unix conventions. If your program is executed from a command line interface, the value returned by main can be used to indicate success or failure, and that value can be used by a shell script.