[Python-ideas] Implement comparison operators for range objects

[Sven Marnach]

Nick Coghlan schrieb am Do, 13. Okt 2011, um 11:43:53 +1000:
> I'll weigh in on the "compare like a sequence" side, even if the
> specific range definitions are different. It's the way range
> comparisons work in Python 2 and I'd like range() objects to be as
> close to a computationally defined immutable list as we can get them.
> It may even make sense to make them hashable in those terms.

The current interface of ranges is that of a sequence and nothing
more.  The only place where the original parameters that were used to
create the sequence pop up is in its representation.  Giving those
parameters more weight seems a bit like remembering the list
coomprehension that was used to create a list and take this into
account when comparing lists (of course I'm exaggerating here to make
a point).

> But not exposing start/stop/step is a definite oversight - I actually
> thought we *did* expose them, but I was thinking of slice objects.
> With those attributes exposed, anyone that wants a more restrictive
> form of equality can easily implement it for themselves.

The current implementation of range objects could be both made
considerably shorter and sped up a bit by normalising the parameters
right from the start.  I'd argue that doing so would be a good idea
even when start, stop and step are exposed.  It would make clear what
is happening and remove any ambiguity as to the semantics of range
objects in general and comparison of range objects in particular.  (A
simple implementation is more often than not a good indication for
having arrived at the right notions.)

Note that using '[:]' does not completely normalise a range object.
It only normalises the stop parameter.

Cheers,
    Sven