python - Can I use information of a dict key to define another key of the same dict?

Question

What I'd like to do is the following:

test_dict = dict(value = 1,
                 property = properties_list[value-1]
                )

Naturally, I couldn't do it this way, since it throws me an error saying that name 'value' is not defined.

Answer 1

You could do it by using an assignment expression (aka “the walrus operator”) which were introduced in Python 3.8.

properties_list = [42, 13]

test_dict = dict(value=(_:=1), property=properties_list[_-1])

print(test_dict)  # -> {'value': 1, 'property': 42}