tuple.__hash__()

[Thomas Guettler]

Am Tue, 06 Jan 2004 04:04:01 -0500 schrieb Mike C. Fletcher:

> Just wrote:
> AFAIK, the dictionary class simply uses the hash to sort into buckets, 
> providing fast indexing, before using equality to check whether the two 
> keys are equal. 

Thank you, that what I was asking for.

Here is a sample script which checks this:

from types import *

class MyHash:
    def __init__(self, id):
        assert(type(id)==IntType)
        self.id=id

    def __hash__(self):
        # All objects have the same hash value
        return 1

    def __cmp__(self, b):
        return cmp(self.id, b.id)

    def __repr__(self):
        return "<MyHash id=%s>" % self.id
    
def main():
    d={}
    i1=MyHash(1)
    d[i1]=1
    i2=MyHash(2)
    d[i2]=1
    i3=MyHash(3)
    d[i3]=1
    print d.items()

    # id=1 twice
    d[MyHash(1)]=1

    print d.items()
    # All right there are only three elements in the dict
    # Dictionaries use __cmp__ if __hash__ is equal.
    
if __name__=="__main__":
    main()