[Python-Dev] Keep default comparisons - or add a second set? (original) (raw)

Paul Moore p.f.moore at gmail.com
Mon Dec 19 21:19:58 CET 2005

On 12/19/05, Jim Jewett <jimjjewett at gmail.com> wrote:

Unfortunately, one very common use case of comparisons is to get a canonical order. If the order is sensible, all the better, but that is not strictly required. One of Python's selling points (especially compared to Java) is that getting a canonical order "just works", even if the objects being sorted are not carefully homogenized by hand. Python itself relies on this when comparing same-length dictionaries.

While I agree that this is a useful property, and I'd like it to be true, it isn't even today:

import Numeric a = Numeric.array((1,2,3)) a array([1, 2, 3]) sorted([a, (1,2,3), 1, 2, '123']) Traceback (most recent call last): File "", line 1, in ? TypeError: function not supported for these types, and can't coerce to supported types _a < '123'_ Traceback (most recent call last): File "", line 1, in ? TypeError: function not supported for these types, and can't coerce to supported types

Numeric arrays are the canonical example of an "awkward case" when discussing comparisons...

OTOH, I'm not sure I want to see more "awkward cases" added.

Paul.

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