[nmg]

I agree, I use += as shorthand, I wasn't aware it was fundamentally different under the hood.

[disgruntledphd2]

If you like this kind of thing, the python manual has this: https://docs.python.org/3/reference/datamodel.html

I found the book Fluent Python to be a great introduction to the ideas behind abstraction in Python.

Apparently, it's cadged from the Art of the Metaobject Protocol, which is a great book (which annoyingly enough, is not available in ebook form, which is a shame as typing loads of code from a dead-tree book is time consuming).