hash values and equality

[Steven D'Aprano]

On Sat, 21 May 2011 15:55:56 -0700, John Nagle wrote:

> On 5/19/2011 11:33 PM, Ulrich Eckhardt wrote:
> 
>> For that reason, it is generally useful to use immutable types like
>> integers, floats, strings and tuples thereof as keys. Since you can't
>> change them, you basically have the guarantee that they hash the same.
> 
>     Right.  It's something of a lack that Python doesn't
> have user-defined immutable objects.


Although it's not that hard to write your own immutable (-ish) objects.

http://northernplanets.blogspot.com/2007/01/immutable-instances-in-python.html


Or see the Decimal and Fraction classes in the standard library.


-- 
Steven