[Python-ideas] Add "equal" builtin function

[אלעזר]

It is a real problem. People are used to write `seq == [1, 2, 3]` and it
passes unnoticed (even with type checkers) that if seq changes to e.g. a
tuple, it will cause subtle bugs. It is inconvenient to write `len(seq) ==
3 and seq == [1, 2, 3]` and people often don't notice the need to write it.

(I'd like to note that it makes sense for this operation to be written as

    *iter1 == *lst

although it requires a significant change to the language, so a
Sequence.equal function makes sense)

Elazar

On Thu, Oct 6, 2016 at 5:02 PM Paul Moore <p.f.moore at gmail.com> wrote:

> On 6 October 2016 at 14:45, Filipp Bakanov <filipp at bakanov.su> wrote:
> > For now there are many usefull builtin functions like "any", "all", etc.
> I'd
> > like to propose a new builtin function "equal". It should accept
> iterable,
> > and return True if all items in iterable are the same or iterable is
> emty.
> > That's quite popular problem, there is a discussion of how to perform it
> on
> > stackoverflow
> > (
> http://stackoverflow.com/questions/3844801/check-if-all-elements-in-a-list-are-identical
> )
> > - all suggestions are either slow or not very elegant.
> > What do you think about it?
>
> It's not a problem I've needed to solve often, if at all (in
> real-world code). But even if we assume it is worth having as a
> builtin, what would you propose as the implementation? The
> stackoverflow discussion highlights a lot of approaches, all with
> their own trade-offs. One problem with a builtin is that it would have
> to work on all iterables, which is likely to preclude a number of the
> faster solutions (which rely on the argument being an actual list).
>
> It's an interesting optimisation problem, and the discussion gives
> some great insight into how to micro-optimise an operation like this,
> but I'd question whether it needs to be a language/stdlib feature.
>
> Paul
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