Creating a namedtuple with a custom hash function

I think there is something wrong with your code (my guess is that you created an instance of the tuple with the same name, so fooTuple is now a tuple, not a tuple class), because subclassing the named tuple like that should work. Anyway, you don't need to redefine the constructor. You can just add the hash function:

In [1]: from collections import namedtupleIn [2]: Foo = namedtuple('Foo', ['item1', 'item2'], verbose=False)In [3]: class ExtendedFoo(Foo):   ...:     def __hash__(self):   ...:         return hash(self.item1) * hash(self.item2)   ...: In [4]: foo = ExtendedFoo(1, 2)In [5]: hash(foo)Out[5]: 2

Starting in Python 3.6.1, this can be achieved more cleanly with the typing.NamedTuple class (as long as you are OK with type hints):

from typing import NamedTuple, Anyclass FooTuple(NamedTuple):    item1: Any    item2: Any    def __hash__(self):        return hash(self.item1) * hash(self.item2)

A namedtuple with a custom __hash__ function is useful to store immutable data models into dict and set

For example:

class Point(namedtuple('Point', ['label', 'lat', 'lng'])):    def __eq__(self, other):        return self.label == other.label    def __hash__(self):        return hash(self.label)    def __str__(self):        return ", ".join([str(self.lat), str(self.lng)])

Override both __eq__ and __hash__ allows grouping businesses into a set, ensuring that each business line is unique in the collection:

walgreens = Point(label='Drugstore', lat = 37.78735890, lng = -122.40822700)mcdonalds = Point(label='Restaurant', lat = 37.78735890, lng = -122.40822700)pizza_hut = Point(label='Restaurant', lat = 37.78735881, lng = -122.40822713)businesses = [walgreens, mcdonalds, pizza_hut]businesses_by_line = set(businesses)assert len(business) == 3assert len(businesses_by_line) == 2