On 2022-08-16 22:14, Barry Scott wrote:
> On 16 Aug 2022, at 21:24, MRAB <pyt...@mrabarnett.plus.com> wrote:
>
> Other regex implementations have escape sequences for horizontal whitespace (`\h` and `\H`) and vertical whitespace (`\v` and `\V`).
>
> The regex module already supports `\h`, but I can't use `\v` because it represents `\0x0b', as it does in the re module.
You seem to be mixing the use \ as the escape for strings and the \ that re
uses.
Is it the behaviour that '\<unknown>' becomes '\\<unknown>' that means this is
a breaking change?
Won't this work?
```
re.compile('\v:\\v')
# which is the same as
re.compile(r'\x0b:\v')
```
Some languages, e.g. Perl, have a dedicated syntax for writing regexes,
and they take `\n` (a backslash followed by 'n') to mean "match a newline".
Other languages, including Python, use string literals and can contain
an actual newline, but they also take `\n` (a backslash followed by 'n')
to mean "match a newline".
Thus:
>>> print(re.match('\n', '\n')) # Literal newline.
<re.Match object; span=(0, 1), match='\n'>
>>> print(re.match('\\n', '\n')) # `\n` sequence.
<re.Match object; span=(0, 1), match='\n'>
On the other hand:
>>> print(re.match('\b', '\b')) # Literal backspace.
<re.Match object; span=(0, 1), match='\x08'>
>>> print(re.match('\\b', '\b')) # `\b` sequence, which means a word
boundary.
None
>>>
The problem is that the re and regex modules already have the `\v` (a
backslash followed by 'v') sequence to mean "match the '\v' character", so:
re.compile('\v')
and:
re.compile('\\v')
mean exactly the same.
> Now that someone has asked for it, I'm trying to find a nice way of adding
it, and I'm currently thinking that maybe I could use `\y` and `\Y` instead as
they look a little like `\v` and `\V`, and, also, vertical whitespace is sort-of
in the y-direction.
>
> As far as I can tell, only ProgressSQL uses them, and, even then, it's for what everyone else writes as `\b` and `\B`.
>
> I want the regex module to remain compatible with the re module, in case they get added there sometime in the future.
>
> Opinions?
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