[Python-ideas] Dict with inverse form

[Chris Barker]

the other restriction is that both keys and values (or is it values and
keys?) both need to be immutable.

but yes, I've needed this a lot, and I think that fact that both sets of
keys need to be unique isn't really a restriction -- if you need to look it
up either way, then it's probably naturally a one-to-one mapping anyway.

I've needed this a few times, and have always kludged something together,
rather than make a proper, robust tested class. So I look forward to seeing
what you come up with.

-CHB




On Fri, Feb 12, 2016 at 5:27 AM, João Bernardo <jbvsmo at gmail.com> wrote:

>
> On Fri, Feb 12, 2016 at 2:07 AM, Andrew Barnert <abarnert at yahoo.com>
> wrote:
>>
>> For example, when I've built something like this, sometimes I want errors
>> on duplicate values, sometimes just pick one arbitrarily, sometimes I want
>> the inverse dict to store sets of values, and sometimes I even want _both_
>> to store sets of values. Do you want to do just one of those, or two or
>> more? Controlled by flags? Or different attribute names? Or different
>> classes?
>>
>
> My use case is quite simple. I believe I always used this pattern on a
> one-to-one mapping, so allowing repeated values to overwrite or throwing an
> error is not exactly important to me, but it may be to someone else.
>
> Someone suggested a MultiDict sort of thing, but I don't think I need that
> amount of complexity here.
>
> I will write a concrete class and post on PyPI then.
>
> João Bernardo
>
>
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