Python __hash__ return value - what use is it?

Veek M <[email protected]> Sun, 31 May 2026 08:28:46 -0000 (UTC)
Newsgroups comp.lang.python
Organization A noiseless patient Spider
Message-ID <[email protected]>
1. So I am returning 1 for every instance of MyClass and then inserting 
the instances into a set. However when I print the set I see individual 
instances though I want the instances to be the treated the same .ie there 
should be just one instance in the set because the return value from 
__hash__ is always 1.

In the dictionary when I print it I see the instances as individual keys 
though I want to see a single key - what gives?? Why is the return value 
of __hash__ being ignored?? (I can see it's being called)

2. When is __eq__ used? If I have two instances and want to make them 
equal - what's the use case?

#!/usr/bin/python

class MyClass:
    def __bool__(self):
        print('in __bool__')
        return True

    def __hash__(self):
        # hash value is not a key
        print('in __hash__')
        return 1

    def __eq__(self, val):
        print('in __eq__', val)
        return True

c = MyClass()
d = MyClass()

if c:
    print("true")

print('-----')
s = set()
s.add(c)
s.add(d)
print(s)

print('-----')
d = { c : "10", d : "20"  }
print(d)