[Python-ideas] Delayed Execution via Keyword

[Joseph Jevnik]

There is no existing code that uses delayed execution so we don't need to
worry about breaking it. I think it would be much easier to reason about if
forcing an expression was always explicit. I am not sure what you mean with
the second case; why are you delaying a function if you care about the
observable side-effect?

On Fri, Feb 17, 2017 at 4:14 PM, Ed Kellett <edk141 at gmail.com> wrote:

> On Fri, 17 Feb 2017 at 19:38 Joseph Jevnik <joejev at gmail.com> wrote:
>
>> Delayed execution and respecting mutable semantics seems like a
>> nightmare. For most indexers we assume hashability which implies
>> immutability, why can't we also do that here? Also, why do we need to
>> evaluate callables eagerly?
>>
>
> Respecting mutability: we just have to always, we don't know if a delayed
> thing is hashable until we evaluate it. This thing has implications for
> existing code (since delayed objects can get anywhere) so it should be
> careful not to do anything too unpredictable, and I think d[k] meaning
> "whatever is in d[k] in five minutes' time" is unpredictable. One can
> always delay: d[k] if it's wanted.
>
> Evaluate calls: because if you don't, there's no way to say "strictly
> evaluate x() for its side effects".
>
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