Re: Code improvement question
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.
hp
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|_|_) ||
| | | h...@hjp.at |-- Charles Stross, "Creative writing
__/ | http://www.hjp.at/ | challenge!"
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Re: Code improvement question
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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Re: Code improvement question
On 2023-11-17 07:48:41 -0500, Thomas Passin via Python-list wrote:
> On 11/17/2023 6:17 AM, Peter J. Holzer via Python-list wrote:
> > 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.
> >
[...]
> > > > > 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
Yes. That's what I alluded to above.
hp
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|_|_) ||
| | | h...@hjp.at |-- Charles Stross, "Creative writing
__/ | http://www.hjp.at/ | challenge!"
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Re: Code improvement question
On 11/17/2023 9:46 AM, Peter J. Holzer via Python-list wrote:
On 2023-11-17 07:48:41 -0500, Thomas Passin via Python-list wrote:
On 11/17/2023 6:17 AM, Peter J. Holzer via Python-list wrote:
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.
[...]
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
Yes. That's what I alluded to above.
I know, and I just wanted to make it explicit for people who didn't know
much about Python regexes.
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Re: Code improvement question
Mike Dewhirst ha scritto:
On 15/11/2023 10:25 am, MRAB via Python-list wrote:
On 2023-11-14 23:14, Mike Dewhirst via Python-list wrote:
I'd like to improve the code below, which works. It feels clunky to me.
I need to clean up user-uploaded files the size of which I don't know in
advance.
After cleaning they might be as big as 1Mb but that would be super rare.
Perhaps only for testing.
I'm extracting CAS numbers and here is the pattern xx-xx-x up to
xxx-xx-x eg., 1012300-77-4
def remove_alpha(txt):
""" r'[^0-9\- ]':
[^...]: Match any character that is not in the specified set.
0-9: Match any digit.
\: Escape character.
-: Match a hyphen.
Space: Match a space.
"""
cleaned_txt = re.sub(r'[^0-9\- ]', '', txt)
bits = cleaned_txt.split()
pieces = []
for bit in bits:
# minimum size of a CAS number is 7 so drop smaller clumps
of digits
pieces.append(bit if len(bit) > 6 else "")
return " ".join(pieces)
Many thanks for any hints
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.
That little re.sub() came from ChatGPT and I can understand it without
too much effort because it came documented
I suppose ChatGPT is the answer to this thread. Or everything. Or will be.
Thanks
Mike
I respect your opinion but from the point of view of many usenet users
asking a question to chatgpt to solve your problem is truly an overkill.
The computer world overflows with people who know regex. If you had not
already had the answer with the use of 're' I would have sent you my
suggestion that as you can see it is practically identical. I am quite
sure that in this usenet the same solution came to the mind of many
people.
with open(file) as fp:
try: ret = re.findall(r'\b\d{2,7}\-\d{2}\-\d{1}\b', fp.read())
except: ret = []
The only difference is '\d' instead of '[0-9]' but they are equivalent.
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Re: Code improvement question
On 2023-11-17 09:38, jak via Python-list wrote:
Mike Dewhirst ha scritto:
On 15/11/2023 10:25 am, MRAB via Python-list wrote:
On 2023-11-14 23:14, Mike Dewhirst via Python-list wrote:
I'd like to improve the code below, which works. It feels clunky to me.
I need to clean up user-uploaded files the size of which I don't know in
advance.
After cleaning they might be as big as 1Mb but that would be super rare.
Perhaps only for testing.
I'm extracting CAS numbers and here is the pattern xx-xx-x up to
xxx-xx-x eg., 1012300-77-4
def remove_alpha(txt):
""" r'[^0-9\- ]':
[^...]: Match any character that is not in the specified set.
0-9: Match any digit.
\: Escape character.
-: Match a hyphen.
Space: Match a space.
"""
cleaned_txt = re.sub(r'[^0-9\- ]', '', txt)
bits = cleaned_txt.split()
pieces = []
for bit in bits:
# minimum size of a CAS number is 7 so drop smaller clumps
of digits
pieces.append(bit if len(bit) > 6 else "")
return " ".join(pieces)
Many thanks for any hints
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.
That little re.sub() came from ChatGPT and I can understand it without
too much effort because it came documented
I suppose ChatGPT is the answer to this thread. Or everything. Or will be.
Thanks
Mike
I respect your opinion but from the point of view of many usenet users
asking a question to chatgpt to solve your problem is truly an overkill.
The computer world overflows with people who know regex. If you had not
already had the answer with the use of 're' I would have sent you my
suggestion that as you can see it is practically identical. I am quite
sure that in this usenet the same solution came to the mind of many
people.
with open(file) as fp:
try: ret = re.findall(r'\b\d{2,7}\-\d{2}\-\d{1}\b', fp.read())
except: ret = []
The only difference is '\d' instead of '[0-9]' but they are equivalent.
Bare excepts are a very bad idea.
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Re: Code improvement question
MRAB ha scritto: Bare excepts are a very bad idea. I know, you're right but to test the CAS numbers were inside a string (txt) and instead of the 'open(file)' there was 'io.StingIO(txt)' so the risk was almost null. When I copied it here I didn't think about it. Sorry. -- https://mail.python.org/mailman/listinfo/python-list
RE: Code improvement question
Many features like regular expressions can be mini languages that are designed
to be very powerful while also a tad cryptic to anyone not familiar.
But consider an alternative in some languages that may use some complex set of
nested function calls that each have names like match_white_space(2, 5) and
even if some are set up to be sort of readable, they can be a pain. Quite a few
problems can be solved nicely with a single regular expression or several in a
row with each one being fairly simple. Sometimes you can do parts using some of
the usual text manipulation functions built-in or in a module for either speed
or to simplify things so that the RE part is simpler and easier to follow.
And, as noted, Python allows ways to include comments in RE or ways to specify
extensions such as PERL-style and so on. Adding enough comments above or within
the code can help remind people or point to a reference and just explaining in
English (or the language of your choice that hopefully others later can
understand) can be helpful. You can spell out in whatever level of detail what
you expect your data to look like and what you want to match or extract and
then the RE may be easier to follow.
Of course the endless extensions added due to things like supporting UNICODE
have made some RE much harder to create or understand and sometimes the result
may not even be what you expected if something strange happens like the symbols
①❹⓸
The above might match digits and maybe be interpreted at some point as 12
dozen, which may even be appropriate but a bit of a surprise perhaps.
-Original Message-
From: Python-list On
Behalf Of Peter J. Holzer via Python-list
Sent: Friday, November 17, 2023 6:18 AM
To: python-list@python.org
Subject: Re: Code improvement question
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.
hp
--
_ | Peter J. Holzer| Story must make more sense than reality.
|_|_) ||
| | | h...@hjp.at |-- Charles Stross, "Creative writing
__/ | http://www.hjp.at/ | challenge!"
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