replacing `else` with `then` in `for` and `try`

[Chris Angelico]

On Thu, Nov 2, 2017 at 7:05 PM, Alexey Muranov <alexey.muranov at gmail.com> wrote:
> On Wed, 2017-11-01 at 21:30 +0000, Stefan Ram wrote:
>>
>> >
>> >   In languages like Algol 68, »then« is used for a clause
>> >   that is to be executed when the main condition of an
>> >   if-statement /is/ true, so this might cause some confusion.
>> >
>
>
> sure, and `else` is used for a clause that is to be executed when the main
> condition of `if` is false.
>
> So, in
>
>    try:
>        do_something
>    except:
>        catch_exception
>    else:
>        continue_doing_something
>
> when no exception occurs in `do_something`, is `do_something` more true, or
> more false?

It's neither. It didn't happen. That's the whole point of exceptions -
they aren't about normal flow and normal values, they are
fundamentally different. But if you like, consider this kind of model:

caught_exception = catch {{{
    do_something
}}}
if caught_exception is not None:
    handle_exception
else:
    continue_doing_something

The caught exception is either a thing, or not a thing.

ChrisA