Re: Passing arguments to function - (The fundamentals are confusing me)

Gregory Piñero wrote:
Ahh, so it's a mutable thing. That makes sense that I can't change a
mutable object and thus can't affect it outside of the function. 

If you meant "immutable" for the second mutable, you're right.

Does
that mean Python functions aren't always byref, but are sometimes
byval for nonmutables?

It'd probably do you good to get away from the by reference/by value thinking. Python isn't C/Basic/Fortran/etc.

Variables in Python are names. They aren't the cubbyholes into which you put values, they are sticky notes on the front of the cubby hole.

Parameter passing in Python always work the same way - you create a new name pointing to the passed object. Fin.

The confusion you're having isn't in parameter passing, it's in the difference between assignment and mutation. Mutation changes the object itself (what's in the cubby hole), so it doesn't matter what or how many names/variables it has (what sticky notes are on the front). Assigment just changes where names point, not the contents of objects. (It's moving that sticky note, and only that sticky note, from one cubby to a different one.) Assignment justs affects that name, not any other name which point to the same object, including the variables in the passing scope.
.

Relevant Pages