Modern Python Standard Library Cookbook

How to do it...

The itertools module is again a very powerful tool that provides us with the foundations we need to handle iterables:

import itertools

def group_by_key(iterable, key):
    iterable = sorted(iterable, key=key)
    return {k: list(g) for k,g in itertools.groupby(iterable, key)}

Given our list of names, we can apply a key function that grabs the first character of the name so that all entries will be grouped by it:

>>> group_by_key(names, lambda v: v[0][0])
{'A': [('Alex', 'Zanardi'), ('Anakin', 'Skywalker')], 
 'J': [('Julius', 'Caesar'), ('Joseph', 'Joestar')]}