On Sat, Dec 12, 2020 at 11:42 AM Jonathan Crall <erote...@gmail.com> wrote:
>
> I'm not sure if this has been asked / suggested before.
>
> I'm wondering if there is any interest in conditional or loop-based `with`
> statements. I think it could be done without a syntax change.
>
> ### Napkin proposal
>
> Context managers could define `__if__` or `__for__`, and if those dunder
> methods were defined, then the `with` statement would either behave like a
> conditional or a loop.
>
> If `__if__` was defined then
>
> ```
> with Ctx():
> print('hi')
> ```
>
> would only print `hi` if `__if__` returned True. This doesn't require a
> syntax change.
This part has been proposed before:
https://www.python.org/dev/peps/pep-0377/
> The `__for__` variant would likely need a minor syntax change.
>
> ```
> with item in Ctx():
> print(item)
> ```
>
> The `__for__` method is a generator that generates arguments of a loop. The
> item will be printed as many times as there are items generated by `__for__`.
>
Not sure that this one has, but it's basically just a context manager
and a for loop, so I'm not really sure how much you'd gain over just
using the two constructs independently, given that there'd then be
massive confusion over "when should I use 'with item in thing' and
when should I use 'for item in thing'?".
For many use cases, it may be best to write the body as a function,
which can then be called more than once. You can decorate a function
in order to do whatever you like, and the return value from the
decorator could be whatever stats you want to provide (there's no rule
says that a function decorator has to return a function!).
ChrisA
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