Groups > comp.lang.python > #197795

Re: Python hash return value - what use is it?

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From	ram@zedat.fu-berlin.de (Stefan Ram)
Newsgroups	comp.lang.python
Subject	Re: Python __hash__ return value - what use is it?
Date	31 May 2026 09:40:07 GMT
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Veek M <veekjunk@foobar.com> wrote or quoted:
>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.

  I used the code below, where I added statements to print lengths,
  and all lengths printed are always "1" for me.

  Python Code

#!/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); print( "len( s )= ", len( s ))
s.add(d); print( "len( s )= ", len( s ))
print(s)

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

  Python Output (abbreviated at "...")

in __bool__
true
-----
in __hash__
len( s )=  1
in __hash__
in __eq__ <__main__.MyClass object at ...>
len( s )=  1
{<__main__.MyClass object at ...>}
-----
in __hash__
in __hash__
in __eq__ <__main__.MyClass object at ...>
len( d )=  1
{<__main__.MyClass object at ...>: '20'}

Thread

Python __hash__ return value - what use is it? Veek M <veekjunk@foobar.com> - 2026-05-31 08:28 +0000
  Re: Python __hash__ return value - what use is it? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-31 09:25 +0000
    Re: Python __hash__ return value - what use is it? Veek M <veekjunk@foobar.com> - 2026-05-31 10:13 +0000
  Re: Python __hash__ return value - what use is it? ram@zedat.fu-berlin.de (Stefan Ram) - 2026-05-31 09:40 +0000
  Re: Python __hash__ return value - what use is it? Jon Ribbens <jon+usenet@unequivocal.eu> - 2026-05-31 13:06 +0000

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