Accessing a dictionary member within the same dictionary

Question

I am trying to do something like this:

_dict = {"foo" : 1234,
         "bar" : _dict["foo"] + 1}

Cant seem to get the syntax correct, is there a way to acomplish this without using multiple dictionaries, or defining them elsewhere?

Answer 1

You cannot access _dict while defining it. Python first evaluates the {...} dict literal before assigning it to _dict. In other words, while evaluating the {...} dict literal statement, _dict is not yet defined and thus cannot be accessed.

Do this instead:

_dict = {"foo" : 1234}
_dict["bar"] = _dict["foo"] + 1