On Sat, 09 Oct 2010 21:39:51 +0100, Arnaud Delobelle wrote: > 1. hash() is an idempotent function, i.e. hash(hash(x)) == hash(x) hold > for any hashable x (this is a simple consequence of the fact that > hash(x) == x for any int x (by 'int' I mean 2.X int)).
It's a beautiful theory, but, alas, it is not the case. >>> hash(-1) == -1 False >>> hash(2**64) == 2**64 False to give only two of an infinite number of counter-examples. Aside: what do you mean by '2.x int'? Do you mean an int in 2.x versions before, or after, ints and longs were partially integrated? [st...@sylar ~]$ python2.1 Python 2.1.3 (#1, Aug 12 2010, 01:53:57) [GCC 4.1.2 20070925 (Red Hat 4.1.2-27)] on linux2 Type "copyright", "credits" or "license" for more information. >>> 2**64 Traceback (most recent call last): File "<stdin>", line 1, in ? OverflowError: integer exponentiation >>> People keep forgetting that 2.2 introduced nearly as many far-reaching changes as 3.0. -- Steven -- http://mail.python.org/mailman/listinfo/python-list