Underscore after a variable name in Python


I am deciphering someone else’s code and I see the following:

def get_set_string(set_):
     if PY3:
         return str(set_)
         return str(set_)

Does the underscore AFTER the variable mean anything or is this just a part of the variable’s name and means nothing?

Asked By: nanachan



It means nothing. I believe the one who wrote this wanted a variable name designating a set, but set is a type in Python (which creates a set), so he added the underscore.

Answered By: Israel Unterman

No semantics are associated with a trailing underscore. According to PEP 8, the style guide for Python, users are urged to use trailing underscores in order to not conflict with Python keywords and/or Python built-ins:

single_trailing_underscore_ : used by convention to avoid conflicts with Python keyword, e.g.

Tkinter.Toplevel(master, class_='ClassName')

Using set_ means that the built-in name for sets, i.e set, won’t get shadowed and lose its known reference during the function call.