Having an operand blank or all whitespace is not a common use case for
join, nor would it be for my proposed '&' operator. I wanted to present
a clear definition, and however I chose it, those corner cases would be
non-obvious.
That said, I have now withdrawn this proposal due to objections by Bruce
Leban and others.
Best wishes
Rob Cliffe
On 11/03/2023 17:13, Antoine Rozo wrote:
It's not that tricky to have the lstrip/rstrip behaviour with a join:
def space_join(*args):
first, *middle, last = args
return ' '.join((first.rstrip(), *(s.strip() for s in middle),
last.lstrip()))
What is harder is to be sure that this would be the expected behaviour
when using a `&` operator on strings.
Why `' a' & 'b'` would produce `'a b'` and `' ' & 'b'` produce `'
b'` for example?
Le sam. 11 mars 2023 à 10:04, Rob Cliffe via Python-ideas
<python-ideas@python.org> a écrit :
On 07/03/2023 09:54, Valentin Berlier 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.
As Steven d'Aprano pointed out re a similar suggestion, this is
not the
same as my proposal, where
" foo " & " bar " & " something "
would evaluated to
" foo bar something "
Far from stripping the left side over and over, it doesn't strip
it at
all! (Or the right side.)
This is trickier to write using join. And if the first or last
string
can be blank, or all whitespace, it is trickier still.
As it is so easy to get these things wrong, perhaps having it
built in
is not such a terrible idea?😁
Best wishes
Rob Cliffe
>
> 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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Antoine Rozo
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