Question

In python:

>>> a = b or {}

Answer 1

I don’t think it has an official name, it’s just a clever/lazy way to be concise. It’s roughly equivalent to:

a = b if b else {}

or:

if b:
    a = b
else:
    a = {}

I wrote this as a comment but I think it’s worth mentioning here:

You have to be very careful when using this trick. If your intention is to set a default value when something is None, it would be better to write that is None test explicitly than use this trick. The reason is that None is not the only thing that evaluates to false in a boolean context. 0, [], {}, … also evaluate to false. So this trick might not give you the expected results if you didn’t think about these special cases.

Here’s one way to do it that is safer:

a = b if b is not None else {}