[Python-ideas] float('∞')=float('inf')

[Joshua Landau]

On 14 July 2013 02:24, Steven D'Aprano <steve at pearwood.info> wrote:
> On 14/07/13 03:25, Philipp A. wrote:
>>
>> so don’t be silly everyone. the question is if float('∞') should work and
>> i
>> say “why the hell not”
>
>
>
> Firstly, let me say that I personally love the idea of float('∞') working.
> Or even having literal ∞ recognised as float('inf') (or perhaps that should
> be Decimal('inf')?).
>
> But I'm still voting -1 on this proposal. If the best argument in favour is
> "why the hell not?", then whatever benefit we might gain is truly tiny. So
> tiny that the benefit is probably smaller than the cost. And yes, there is a
> cost, there is always a cost. There are one-off costs:


That wasn't the best reason. The best reason was given by the OP, who
said that it was for data input. If you receive data that uses ∞, then
it's useful.

> - somebody has to program this feature;
> - write tests for it;
> - write documentation;
>
> and on-going costs:
>
> - that's one more thing for every user to learn;

Doesn't apply here.

> - programmers will have to take this feature into account whenever they use
> float.

This isn't true -- most uses of float(...) don't care about the
internationalisation aspect either. Only a minority of cases will need
to account for this.

> Now, you might argue, and I will agree, that these costs are probably tiny
> costs. But the benefit is even tinier.
>
> Cost: tiny, but real;
> Benefit: "why the hell not?"
> Overall benefit: negative.

With these changes:

Cost: People keep giving bad criticisms
Benefit: Tiny
Overall benefit: Still can't decide

> Here is a simple implementation that supports ∞, +∞ and -∞.
>
>
> _float = float
>
> def float(arg):
>     if isinstance(arg, str):
>         arg = arg.replace('∞', 'inf')
>     return _float(arg)
>
>
> Hands up anyone who already uses this, or something like it, in their code?
> Anyone? Given how trivial it is to build this functionality if you need it,
> if you haven't already done so, chances are that you don't need it, even if
> you think you want it.

I'd hope not, because that's broken code. All the more reason to
accept the proposal.