On 11/17/2023 6:17 AM, Peter J. Holzer via Python-list wrote:
On 2023-11-16 11:34:16 +1300, Rimu Atkinson via Python-list wrote:
Why don't you use re.findall?
re.findall(r'\b[0-9]{2,7}-[0-9]{2}-[0-9]{2}\b', txt)
I think I can see what you did there but it won't make sense to me - or
whoever looks at the code - in future.
That answers your specific question. However, I am in awe of people who
can just "do" regular expressions and I thank you very much for what
would have been a monumental effort had I tried it.
I feel the same way about regex. If I can find a way to write something
without regex I very much prefer to as regex usually adds complexity and
hurts readability.
I find "straight" regexps very easy to write. There are only a handful
of constructs which are all very simple and you just string them
together. But then I've used regexps for 30+ years, so of course they
feel natural to me.
(Reading regexps may be a bit harder, exactly because they are to
simple: There is no abstraction, so a complicated pattern results in a
long regexp.)
There are some extensions to regexps which are conceptually harder, like
lookahead and lookbehind or nested contexts in Perl. I may need the
manual for those (especially because they are new(ish) and every
language uses a different syntax for them) or avoid them altogether.
Oh, and Python (just like Perl) allows you to embed whitespace and
comments into Regexps, which helps readability a lot if you have to
write long regexps.
You might find https://regex101.com/ to be useful for testing your regex.
You can enter in sample data and see if it matches.
If I understood what your regex was trying to do I might be able to suggest
some python to do the same thing. Is it just removing numbers from text?
Not "removing" them (as I understood it), but extracting them (i.e. find
and collect them).
re.findall(r'\b[0-9]{2,7}-[0-9]{2}-[0-9]{2}\b', txt)
\b - a word boundary.
[0-9]{2,7} - 2 to 7 digits
- - a hyphen-minus
[0-9]{2} - exactly 2 digits
- - a hyphen-minus
[0-9]{2} - exactly 2 digits
\b - a word boundary.
Seems quite straightforward to me. I'll be impressed if you can write
that in Python in a way which is easier to read.
And the re.VERBOSE (also re.X) flag can always be used so the entire
expression can be written line-by-line with comments nearly the same as
the example above
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