attrgetter for custom class fields

attrgetter.py

"""
[User(1), User(10), User(19), User(29)]
[User(1), User(10), User(19), User(29)]
"""
from operator import attrgetter

class User:
	def __init__(self, user_id):
		self.user_id = user_id

	def __repr__(self):
		return "User({})".format(self.user_id)

users = [User(19), User(29), User(1), User(10)]
sorted_users = sorted(users, key=lambda u: u.user_id)
attr_sorted_users = sorted(users, key=attrgetter("user_id"))