On Wed, 16 Feb 2022 at 14:47, Valentin Berlier <berlie...@gmail.com> wrote:
>
> Hi,
>
> I've been thinking that it would be nice if regex match objects could be
> deconstructed with pattern matching. For example, a simple .obj parser could
> use it like this:
>
> match re.match(r"(v|f) (\d+) (\d+) (\d+)", line):
> case ["v", x, y, z]:
> print("Handle vertex")
> case ["f", a, b, c]:
> print("Handle face")
>
> Sequence patterns would extract groups directly. Mapping patterns could be
> used to extract named groups, which would be nice for simple
> parsers/tokenizers:
>
> match re.match(r"(?P<number>\d+)|(?P<add>\+)|(?P<mul>\*)", line):
> case {"number": str(value)}:
> return Token(type="number", value=int(value))
> case {"add": str()}:
> return Token(type="add")
> case {"mul": str()}:
> return Token(type="mul")
>
> Right now, match objects aren't proper sequence or mapping types though, but
> that doesn't seem too complicated to achieve. If this is something that
> enough people would consider useful I'm willing to look into how to implement
> this.
I'm not sure I really see the benefit of this, but if you want to do
it, couldn't you just write a wrapper?
>>> class MatchAsSeq(Sequence):
... def __getattr__(self, attr):
... return getattr(self.m, attr)
... def __len__(self):
... return len(self.m.groups())
... def __init__(self, m):
... self.m = m
... def __getitem__(self, n):
... return self.group(n+1)
...
>>> line = "v 1 12 3"
>>> match MatchAsSeq(re.match(r"(v|f) (\d+) (\d+) (\d+)", line)):
... case ["v", x, y, z]:
... print("Handle vertex")
... case ["f", a, b, c]:
... print("Handle face")
...
Handle vertex
Paul
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