simple grouping function in Python

grouping.py

from collections import defaultdict

__all__ = 'group_by', 'index_by'

def group_by(iterable, key):
	grouped = defaultdict(list)
	for item in iterable:
		grouped[key(item)].append(item)
	return grouped

def index_by(iterable, key):
	indexed = {}
	for item in iterable:
		indexed[key(item)] = item
	return indexed