[Python-ideas] Implement comparison operators for range objects

Westley Martínez anikom15 at gmail.com
Fri Oct 14 20:15:38 CEST 2011

On Wed, Oct 12, 2011 at 05:31:44PM +0100, Sven Marnach wrote:
> There are circumstances, for example in unit testing, when it might be
> useful to check if two range objects describe the same range.
> Currently, this can't be done using the '==' operator:
>     >>> range(5) == range(5)
>     False
> To get a useful comparison, you would either need to realise both
> range objects as lists or use a function like
>     def ranges_equal(r0, r1):
>         if not r0:
>             return not r1
>         return len(r0) == len(r1) and r0[0] == r1[0] and r0[-1] == r1 [-1]
> All other built-in sequence types (that is bytearray, bytes, list,
> str, and tuple) define equality by "all items of the sequence are
> equal".  I think it would be both more consistent and more useful if
> range objects would pick up the same semantics.
> When implementing '==' and '!=' for range objects, it would be natural
> to implement the other comparison operators, too (lexicographically,
> as for all other sequence types).  This change would be backwards
> incompatible, but I very much doubt there is much code out there
> relying on the current behaviour of considering two ranges as unequal
> just because they aren't the same object (and this code could be
> easily fixed by using 'is' instead of '==').
> Opinions?

I'm -32767 on this whole idea.  It's not obvious what comparing a range
actually means, because a range is very abstract.  If a developer needs
to compare ranges they should write their own functions to do it in
whatever way that fits their case.

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