Modern Python Standard Library Cookbook

Grouping similar items

Sometimes you might face a list of entries that has multiple, repeated entries and you might want to group the similar ones based on some kind of property.

For example, here is a list of names:

names = [('Alex', 'Zanardi'),
         ('Julius', 'Caesar'),
         ('Anakin', 'Skywalker'),
         ('Joseph', 'Joestar')]

We might want to build a group of all people whose names start with the same character, so we can keep our phone book in alphabetical order instead of having names randomly scattered here and there.