为什么无法在Python的`if __name__ ==“ __main __”`中执行return

Question

I am writing a program and I need the program to return a integer say changed to remind the controller that there are something changed.But when I want to return this value, I kept receiving this message:

 return 1
 SyntaxError: 'return' outside function

I have read some posts online they all said it is the indent problem but I am sure My indent is right because I have tried such a simple program but the failure still exists.

# -*- coding: utf-8 -*-


if __name__ == "__main__":
     return 1

here is the error message:

runfile('/home/iphyer/untitled1.py', wdir='/home/iphyer')
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/usr/local/lib/python2.7/dist-packages/spyderlib/widgets/externalshell/sitecustomize.py", line 699, in runfile
 execfile(filename, namespace)
  File "/usr/local/lib/python2.7/dist-packages/spyderlib/widgets/externalshell/sitecustomize.py", line 81, in execfile
builtins.execfile(filename, *where)
  File "/home/iphyer/untitled1.py", line 9
   return 1
  SyntaxError: 'return' outside function

Although my real programe is more complex than this but the structure is the same.

I am confused because if I comment the return statement all program can be run without any warning.

It is quit confusing. I guess I can not using if __name__ == "__main__ for return some value?

Thank you!~

Answer 1

The body of the if __name__ == "__main__": executes when the file in question is being run as a standalone program. In that case, what you may want is exit() or sys.exit() which allow you to return limited information to the script that invoked this one. Typically you can either signal success with exit(0) or set of possible failures with a non-zero result (limited to 1 - 255). return is for subroutines/function, exit is for programs.

Answer 2

Because if statement isn't a method. You can return only from methods in Python.