[Python-ideas] "Exposing" `__min__` and `__max__`

[Michael Selik]

Do you mind sharing an example usage in a realistic context? There might be
a good solution that doesn't require adding magic methods.


On Tue, Jun 19, 2018, 12:24 PM James Edwards <jheiv at jheiv.com> wrote:

> I've only recently looked for these special methods, so that in and of
> itself may be the reason these methods aren't exposed, but I could think of
> objects that may wish to implement __min__ and __max__ themselves, for
> efficiency.  For example:
>
>     # A "self-sorted" list object
>     class AlwaysSortedListObejct:
>         def __min__(self): return self.lst[0]
>         def __max__(self): return self.lst[-1]
>
>
>     # An object that maintains indices of extrema (e.g. for complex
> comparisons)
>     class KeepsTrackOfExtrema:
>         def __init__(self):
>             self.min_index = None
>             self.max_index = None
>
>         def append(self, obj):
>             new_index = len(obj)
>             self.backer.append(obj)
>
>             if (self.max_index is None) or (obj >
> self.backer[self.max_index]):
>                 self.max_index = new_index
>
>             if (self.min_index is None) or (obj <
> self.backer[self.min_index]):
>                 self.min_index = new_index
>
>         def __min__(self): return self.backer[self.min_index]
>         def __max__(self): return self.backer[self.max_index]
>
> Where these methods be called via the single-argument calls to `max(obj)`
> and `min(obj)`.
>
> If it's not clear, it'd be similar to the way __len__ is called (when
> defined) via len(obj).
>
> My solution was to implement a .min() method, but that caused some ugly
> special casing when the object could also be a regular list (where I'd want
> to iterate over all of the items).
>
> I searched the list, but has this been discussed before?  Is there any
> merit in it?
>
> _______________________________________________
> Python-ideas mailing list
> Python-ideas at python.org
> https://mail.python.org/mailman/listinfo/python-ideas
> Code of Conduct: http://python.org/psf/codeofconduct/
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20180619/82c276db/attachment.html>