Monday 2:35 p.m.–3:05 p.m.
Finding closure with closures
Thomas Ballinger
- Audience level:
- Intermediate
- Category:
- Python Core (language, stdlib, etc.)
Description
What are closures all about anyway, and why is there a new keyword in Python
3?
We'll look at what a closure is, their history in the Python language, what
the Python 3 nonlocal keyword is about, and examine how closures are
idiomatically used (and avoided) in Python.
Abstract
Since the release of Python 2.2 in 2001, all Python functions have closed over
bindings in outer scopes. At the time it was a relief not to have to pass in
every variable an inner function might use.
Now thanks to the nonlocal keyword introduced by PEP 3104 we have
rebinding closures in Python 3.
With it you can simplify and clarify code, particularly some types of
callbacks.
I think nonlocal is pretty cool, but its reception has been tepid.
We'll look at why rebinding closures are as necessary in Python
as in other language, but still learn to love this new tool for clarifying our
code. To do this we'll need to look at what closures are and how they're used
in Python.
We'll learn to recognized a variety hacks that we don't need to use anymore in python 3.
PyCon 2016 in Portland, OR is a production of the 