[Python-ideas] Exploiting type-homogeneity in list.sort() (again!)

[David Mertz]

On Tue, Mar 7, 2017 at 6:27 PM, Erik <python at lucidity.plus.com> wrote:

> Good point about list.extend().  I don't think __type_hint__ could help
>> with .__contains__() or .count() or .remove().  E.g.:
>>
>>     In [7]: lst = [1.0, 2.0, 1+0j, F(1,1)]
>>     In [8]: from fractions import Fraction as F
>>     In [9]: lst = [1.0, 2.0, 1+0j, F(1,1)]
>>     In [10]: 1 in lst
>>     Out[10]: True
>>
>> The list has absolutely nothing of the right type.  Yet it contains an
>> item, counts things that are equal, finds a position for an equal item.
>>
>
> Sure, but if the needle doesn't have the same type as the (homogeneous)
> haystack, then the rich comparison would still need to be done as a
> fallback (and would produce the result you indicate).
>

In [22]: class Eq(int):
    def __eq__(self, other):
        return True
   ....:
In [23]: four, five, six = Eq(4), Eq(5), Eq(6)
In [24]: lst = [four, five, six]
In [25]: lst.count(Eq(7))
Out[25]: 3


How would this work (other than saying "don't do that it's perverse")?

-- 
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