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I have a small issue i am running into. I need a regular expression that would split a passed string with numbers separately and anything chunk of characters within square brackets separately and regular set of string separately.

for example if I have a strings that resembles

s = 2[abc]3[cd]ef

i need a list with lst = ['2','abc','3','cd','ef']

I have a code so far that has this..

import re
s = "2[abc]3[cd]ef"
s_final = ""
res = re.findall("(\d+)\[([^[\]]*)\]", s)
print(res)

This is outputting a list of tuples that looks like this.

[('2', 'abc'), ('3', 'cd')]

I am very new to regular expression and learning.. Sorry if this is an easy one.

Thanks!

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  • 3
    re.findall(r'\w+', s)? Or re.findall(r'\d+|[^\W\d_]+', s)? Commented Jul 4, 2021 at 17:03

3 Answers 3

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The immediate fix is getting rid of the capturing groups and using alternation to match either digits or chars other than square bracket chars:

import re
s = "2[abc]3[cd]ef"
res = re.findall(r"\d+|[^][]+", s)
print(res)
# => ['2', 'abc', '3', 'cd', 'ef']

See the regex demo and the Python demo. Details:

  • \d+ - one or more digits
  • | - or
  • [^][]+ - one or more chars other than [ and ]

Other solutions that might help are:

re.findall(r'\w+', s)
re.findall(r'\d+|[^\W\d_]+', s)

where \w+ matches one or more letters, digits, underscores and some more connector punctuation with diacritics and [^\W\d_]+ matches any one or more Unicode letters.

See this Python demo.

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1 Comment

re.findall(r'\d+|[^\W\d_]+', s) this particular case works like a charm! Thanks!
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Don't try a regex that will find all part in the string, but rather a regex that is able to match each block, and \w (meaning [a-zA-Z0-9_]) feats well

s = "2[abc]3[cd]ef"
print(re.findall(r"\w+", s))  # ['2', 'abc', '3', 'cd', 'ef']

Or split on brackets

print(re.split(r"[\[\]]", s))  # ['2', 'abc', '3', 'cd', 'ef ']
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I think like Jonathan is pointing out the string is irregular. If I introduce a string in front of 2, all the solution breaks. for example if my string is s = "sm2[abc]3[cd]ef" the output i get is ['sm2', 'abc', '3', 'cd', 'ef']. Instead it should be ['sm', 2, 'abc', '3', 'cd', 'ef'].
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Regex is intended to be used as a Regular Expression, your string is Irregular. regex is being mostly used to find a specific pattern in a long text, text validation, extract things from text.

for example, in order to find a phone number in a string, I would use RegEx, but when I want to build a calculator and I need to extract operators/digits I would not, but I would rather want to write a python code to do that.

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