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I don't get the order of how things are executed with main() - pythonrookie - Jul-20-2020
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()Quote:This is class
<__main__.user_input object at 0x04A26328>
This is main
RE: I don't get the order of how things are executed with main() - Yoriz - Jul-20-2020
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 spaceThe above is actually wrong, the
print("This is class") happens when the class is defined so is actually thirdYou can use this link to visualise code execution
RE: I don't get the order of how things are executed with main() - deanhystad - Jul-20-2020
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()
RE: I don't get the order of how things are executed with main() - pythonrookie - Jul-21-2020
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.
RE: I don't get the order of how things are executed with main() - deanhystad - Jul-21-2020
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")
RE: I don't get the order of how things are executed with main() - pythonrookie - Jul-21-2020
Thank you deanhystad