Sorry Yashwanthbarad, this isn't a bug, you expect the wrong result.

Augmented assignment for lists is documented to be the same as calling the extend method, which means your AppenedFuncShortHandOperator function modifies the argument list in-place.

The AppenedFuncRegularAssignment simply replaces the *local variable* inside the function with a new list. Since it doesn't return the new list, the new list gets thrown away when the function returns, leaving the original list untouched.

This is not a bug, it is the normal behaviour. If you need help understanding why it works the way it does, and the difference between mutating an object and binding a new object to a local variable, there are many places you can ask for help, such as Stackoverflow, the /learnpython sub-reddit on Reddit, the tutor mailing list and others.

https://mail.python.org/mailman/listinfo/tutor

Good luck!