[Python-ideas] Implement comparison operators for range objects

[Paul Moore]

On 12 October 2011 22:12, Ethan Furman <ethan at stoneleaf.us> wrote:
> Agreed -- comparing repr()s seems like a horrible way to do it.
>
> As far as comparing for equality, there's an excellent answer on
> StackOverflow -- http://stackoverflow.com/questions/7740796
>
> def ranges_equal(a, b):
>  return len(a)==len(b) and (len(a)==0 or a[0]==b[0] and a[-1]==b[-1])

While I'm agnostic on the question if whether range(0,9,2) and
range(0,10,2) are the same, I'd point out that ranges_equal is
straightforward to write and says they are equal. But if you're in the
camp of saying they are not equal, you appear to have no way of
determining that *except* by comparing reprs, as range objects don't
seem to expose their start, step and end values as attributes - unless
I've missed something.

>>> r = range(0,10,2)
>>> dir(r)
['__class__', '__contains__', '__delattr__', '__doc__', '__eq__',
'__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__',
'__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__',
'__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
'__reversed__', '__setattr__', '__sizeof__', '__str__',
'__subclasshook__', 'count', 'index']

Rather than worrying about supporting equality operators on ranges,
I'd suggest exposing the start, step and end attributes and then
leaving people who want them to roll their own equality functions.

Paul.