chapter-13.1-groupby.md

13.1. The groupby() Function

The groupby() function is a function that returns consecutive keys and groups from the iterable.

The groupby() generates an iterator that has key and value pair in which key is the value to be grouped by and value is the iterator again which contains grouped value. Source: https://docs.python.org/3/library/itertools.html#itertools.groupby

Example 1

from itertools import groupby

# example 1
animals = ['Bear', 'Donkey', 'Cat', 'Dog', 'Camel', 'Elephant']
animals = sorted(animals)
values = groupby(animals, lambda x: x[0])
grouped = {k: list(v) for k, v in values}
print(grouped)

Output

{'B': ['Bear'], 'C': ['Camel', 'Cat'], 'D': ['Dog', 'Donkey'], 'E': ['Elephant']}