Is this a bug? (__eq__, __lt__, etc.)

[Edw88253]

The __eq__, __gt__, etc. methods seem to be called more often than necessary
when I compare two objects.  Is this a bug or a feature?  (See transcript
below)  If it's a feature, what's it accomplishing?  E.g., what are the
semantics if __lt__(a,b) returns true the first time and false the second
time?

class A:
    def __init__(self, c): self.c=c
    def __cmp__(s,o):
        print 'cmp', s.c, o.c
        return NotImplemented
    def __eq__(s,o):
        print 'eq', s.c, o.c
        return NotImplemented
    def __lt__(s,o):
        print 'lt', s.c, o.c
        return NotImplemented
    def __gt__(s,o):
        print 'gt', s.c, o.c
        return NotImplemented

>>> (a, b) = (A('a'), A('b'))
>>> a == b
eq a b
eq b a
eq b a
eq a b
cmp a b
cmp b a
0
>>> a < b
lt a b
gt b a
gt b a
lt a b
cmp a b
cmp b a
0

(I sent this question out before as part of a post, but didn't get any
responses, so I thought I'd try again..  I would appreciate it if you could
cc responses to edloper at gradient.cis.upenn.edu, but I'll try to keep an eye
out for responses on the newsgroup too..)

-Edward