Find longest (string) key in dictionary

Question

This question is similar to Python - Find longest (most words) key in dictionary - but I need the pure number of characters.

Example input:

d = {\'gr         


        

Answer 1

>>> d = {'group 1': 1, 'group 1000': 0}
>>> len(max(d, key=len))
10

This solution is the fastest but I prefer the solutions by @eumiro and @ms4py since they do not repeat the len function twice and are more pythonic imo.