Variables and objects in Python: it's pointers all the way down

Trey Hunner

In Python, assignment statements don't copy objects, and data structures don't actually contain objects. These two surprising facts have a lot of interesting consequences and are the reason behind many of Python's design decisions.

In this talk, we'll explore the reference-like nature of Python's variables and objects, noting both the benefits and gotchas involved.

Among other ideas, we'll see that in Python:

• The word "change" is ambiguous
• Copying is usually explicit
• Tuples aren't always immutable

During the process, we'll consider our own mental model of Python.

In Python, it's pointers (or references, names, bindings, or aliases) all the way down.