[Python-ideas] Inline assignments using "given" clauses

[Tim Peters]

[attributions lost - sorry, but I can't get 'em back]
...

>>> Similar to import statements, optional parentheses could be included in
>>> the
>>> grammar, allowing the name bindings to be split across multiple lines:
>>>
>>>    if diff and g > 1 given (
>>>        diff = x - x_base,
>>>        g = gcd(diff, n),
>>>    ):
>>>        return g

>> I'm well behind, but... this! This turns "given" into a +0.8 for me.
>>
>> That's really nice. It reads clearly too.
>>

> That's longer than this:
>
> diff = x - x_base
> g = gcd(diff, n)
> if diff and g > 1:
>     return g
>
> which is already valid.

Since that was my example to begin with, I think it's fair to point
out that they all miss a key part of the original example:  this code
is working with multi-thousand bit integers, and calling gcd() is
expensive.  It was a key point that

    if (diff := x - x_base) and (g := gcd(diff, n)) > 1:
         return g

didn't call gcd() _at all_ unless `diff` was non-zero.  The original
real-life code was:

    diff = x - x_base
    if diff:
        g = gcd(diff, n)
        if g > 1:
            return g