Question

I find myself writing stuff like this too often and it seems too wordy:

obj = my_dict.get('obj')
if obj:
    var = obj

Is there a better way to do this? Maybe in one line?

Answer 1

There’s no clean way to replace this code in one line, because it conditionally binds the name var. In the case that var was already defined, this one-liner is possible:

var = my_dict['obj'] if 'obj' in my_dict and my_dict['obj'] else var

However, this is still slightly different than the original code in case var was not already defined: the one-liner is raising a NameError and the original code just continues with var unbound.

Note that other answers behave differently when the value exists but is falsey.

obj = my_dict.get('obj')
if obj:   # <-- test on truthiness of obj
    # if we are here, it means:
    #   1. my_dict has key 'obj', AND...
    #   2. at least one of the following,
    #        my_dict['obj'].__bool__() returned True (__nonzero__ for Python 2)
    #      OR
    #        my_dict['obj'].__len__() returned result > 0
    #      OR
    #        my_dict['obj'] is not None, and has neither __bool__ nor __len__ defined
    var = obj