I don't get the order of how things are executed with main()

[pythonrookie]

Could someone please explain the order of the execution below? I thought main() is the very first function that get executed but somehow the print statement indicates main() cames at the end.

def main():
    print("This is main")


class user_input():
    print("This is class")

print(user_input())    


if __name__ == "__main__":
    main()

This is class
<__main__.user_input object at 0x04A26328>
This is main

[Yoriz]

def main(): # this is first, it is defined but doesn't do anything until called
    print("This is main") # this is eight
 
 
class user_input(): # this is second, it is defined but doesn't do anything until called
    print("This is class") this is fourth
 
print(user_input()) # this is third and fifth and actions straight away as its a statement and a function call in the global space
 
 
if __name__ == "__main__": # this is sixth and actions straight away as its a conditional statement in the global space
    main() # this is seventh and actions straight away as its a function call in the global space

---

The above is actually wrong, the print("This is class") happens when the class is defined so is actually third
You can use this link to visualise code execution

[deanhystad]

Functions execute in the order they are called. Code executes from top to bottom (unless changed by a loop or an if statement).

In your program the first statement in the program that can run is

print(user_input())

the second statement is

if __name__ == '__main__':
    main()

[pythonrookie]

Thank you very much for the answer deanhystad/Yoriz.

I thought main() is always the very first function to get executed when the script is run directly (not imported) which is the feature of "if __name__ == '__main__':" statement.

[deanhystad]

The purpose of "if __name__ == "__main__:" is to prevent executing statements when the file is imported. If I wanted to use your user_input class I could import your module. When I do this I would not want to run your main() function, and the if __name__ == "__main__" prevents that from happening because your file is no longer the "__main__" file.

As for "main()" always being the first function to get executed, there is nothing special about using "main()" as a function name other than convention. You could call your main function "doit()" or something else, or you could not even have a main function. For example, your module would work exactly the same written this way:

class user_input():
    print("This is class")

print(user_input())    

if __name__ == "__main__":
     print("This is main")

[pythonrookie]

Thank you deanhystad