On Fri, Mar 15, 2019 at 12:25:22PM +0100, Antoine Pitrou wrote:
Yeah, well.... I do think "+=" for lists was a mistake. I *still* have trouble remembering the exact difference between "list +=" and "list.extend" (yes, there is one: one accepts more types than the other... which one it is, and why, I never remember;
Both accept arbitrary iterables, and the documentation suggests that they are the same:
https://docs.python.org/3/library/stdtypes.html#mutable-sequence-types
Perhaps you are thinking of the difference between list + list versus list += iterable?
[...]
There is a virtue to
"""There should be one-- and preferably only one --obvious way to do it"""
"It" here refers to two different things:
"I want to update a dict in place":
The Obvious Way is to use the update method; the fact that += works as well is just a side-effect of the way augmented assignments are defined.
"I want a new dict that merges two existing dicts":
The Obvious Way is to use the merge operator (possibly spelled + but that's not written in stone yet).