I agree. This behavior is too specialized to be implemented as an
operator. + is IME so infrequently used on python strings that we should
take caution when proposing new binary string operators. Two strings to
concat, maybe; three, possibly; four or more, and I reach for join() or
f-strings or anything else. And if we are just joining two or three
strings, that is readable right now as str1.rstrip() + ' ' + str2.lstrip().
A solution that is as extensible as join, no need for operators or
subclasses:
def connect(iterable, /):
it = iter(iterable)
first = next(it, '')
last = next(it, None)
if last is None:
return first
else:
parts = [first.rstrip()]
for this in it:
parts.append(last.strip())
last = this
parts.append(last.lstrip())
return ' '.join(parts)
But I would not advocate for inclusion in the standard lib as there are too
many parameters the user may want to behave differently for them. Keep the
trailing spaces? Leading space? Add spaces when connecting an empty string?
A string that is only whitespace? Operate only on exactly str or the
__str__ value of any object?
Regards,
Jeremiah
On Tue, Mar 7, 2023 at 1:57 AM Valentin Berlier <berlie...@gmail.com> wrote:
> I'm -1 on this. You can easily make a helper that achieves the desired
> syntax. Presenting "human readable data" isn't just about collapsing
> spaces, and having your own helper means that you can adjust the formatting
> to your specific use case if needed (for example with a different
> separator).
>
> from typing import Self
>
> class StripJoin:
> def __init__(self, value: str = "") -> None:
> self.value = value
> def __and__(self, other: str) -> Self:
> other = other.strip()
> separator = bool(self.value and other) * " "
> return StripJoin(f"{self.value}{separator}{other}")
> def __str__(self) -> str:
> return self.value
>
> j = StripJoin()
> print(j & " foo " & " bar " & " something ")
> # Output: "foo bar something"
>
> The example above is more efficient than a possible implementation
> directly on the str builtin as it doesn't strip the left side over and
> over. However it still incurs repeated allocations and encourages a pattern
> that performs badly in loops. With a lot of input you should probably
> accumulate the stripped strings in a list and join them all at once.
>
> In any case I recommend reaching out for a library like Rich (
> https://github.com/Textualize/rich) if you care about formatting the
> output of your program nicely.
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