正则表达式提取整数

Question

I need help in extracting number from a column that store texts. In the text, there can be also some prices that I don't want to extract. As an example, if I have the following text:

text = "I have the following products 4526 and 4. The first one I paid $40 while the second one 30€. 
Here the link for the discount of 3.99: https://www.xysyffd.coom/7574@5757"

My expected result would be

[4526, 4]

Right now what I have used the following regular expression

'(?<![\d.])[0-9]+(?![\d.])'

which is able to discard the 3.99 but still it recognize the prices and the number in the link. Any suggestion on how to update the re?

Answer 1

You can assert a whitspace boundary to the left, and exclude matching a dot followed by a digit or the euro sign.

(?<!\S)\d+\b(?!€|\.\d)

• (?<!\S) Assert not a non whitespace char to the left (A whitespace boundary)
• \d+ Match 1+ digits
• \b A word boundary to prevent a partial match
• (?.€|\.\d) Negative lookahead to assert what is directly to the right is not € or . followed by a digit.

Regex demo | Python demo

Example

import re
 
pattern = r"(?<!\S)\d+\b(?!€|\.\d)"
s = ("I have the following products 4526 and 4. The first one I paid $40 while the second one 30€. \n"
    "Here the link for the discount of 3.99: https://w...content-available-to-author-only...d.coom/7574@5757\n")
 
print(re.findall(pattern, s))

Output

['4526', '4']

Answer 2

Use

(?<!\S)[0-9]+(?!\.\d|[^\s!?.])

See proof .

EXPLANATION

--------------------------------------------------------------------------------
  (?<!                     look behind to see if there is not:
--------------------------------------------------------------------------------
    \S                       non-whitespace (all but \n, \r, \t, \f,
                             and " ")
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  [0-9]+                   any character of: '0' to '9' (1 or more
                           times (matching the most amount possible))
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    \.                       '.'
--------------------------------------------------------------------------------
    \d                       digits (0-9)
--------------------------------------------------------------------------------
   |                        OR
--------------------------------------------------------------------------------
    [^\s!?.]                 any character except: whitespace (\n,
                             \r, \t, \f, and " "), '!', '?', '.'
--------------------------------------------------------------------------------
  )                        end of look-ahead

Python code :

import re
regex = r"(?<!\S)[0-9]+(?!\.\d|[^\s!?.])"
test_str = "I have the following products 4526 and 4. The first one I paid $40 while the second one 30€. \nHere the link for the discount of 3.99: https://www.xysyffd.coom/7574@5757"
matches = re.findall(regex, test_str)
print(matches)

Results : ['4526', '4']