Read only numbers from a string

Question

I seen Q&A like this and this but I still have a problem.

What I want is to get a string that might contain non-digits characters, and I want to only extract 2 numbers from that string. So, if my string is 12 ds d21a I want to extract ['12', '21'].

I tried using:

import re
non_decimal = re.compile(r'[^\d.]+')
non_decimal.sub("",input())

and fed this string 12 123124kjsv dsaf31rn. The result was 12123124 which is nice, but I want the non-digit characters to separate the numbers.

Next I tried to add split - non_decimal.sub("",input().split()). Didn't help.

How can I do that (assuming there is way that does not include scanning the whole string, iterating over it and extracting the digits "manually")?

For more clarification, this is what I want to achieve, in C.

`input_ = '12 123124kjsv dsaf31rn' non_decimal = re.findall(r'[\d.]+', input_)` Does that do the trick? — Vivek Kalyanarangan, Nov 23 '17 at 06:29

score 6 · Accepted Answer · answered Nov 23 '17 at 06:31

6

You want to use re.findall() method in this case -

input_ = '12 123124kjsv dsaf31rn' 
non_decimal = re.findall(r'[\d.]+', input_)

Output -

['12', '123124', '31']

answered Nov 23 '17 at 06:31

Vivek Kalyanarangan

8,951
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score 2 · Answer 2 · answered Nov 23 '17 at 06:46

@Vivek answer will solve your issue.

Here is another approach , Just an opinion :

import re
pattern=r'[0-9]+'
string_1="""12 ds  d21a
12 123124kjsv dsaf31rn"""

match=re.finditer(pattern,string_1)
print([find.group() for find in match])

output:

['12', '21', '12', '123124', '31']

score 1 · Answer 3 · answered Nov 23 '17 at 06:37

If all you want to extract are positive integers, do this :

>>> string = "h3110 23 cat 444.4 rabbit 11 2 dog"
>>> [int(x) for x in string.split() if x.isdigit()]
[23, 11, 2]

Then if you want more conditions and want to include scientific notations too:

import re

# Format is [(<string>, <expected output>), ...]
ss = [("apple-12.34 ba33na fanc-14.23e-2yapple+45e5+67.56E+3",
       ['-12.34', '33', '-14.23e-2', '+45e5', '+67.56E+3']),
      ('hello X42 I\'m a Y-32.35 string Z30',
       ['42', '-32.35', '30']),
      ('he33llo 42 I\'m a 32 string -30', 
       ['33', '42', '32', '-30']),
      ('h3110 23 cat 444.4 rabbit 11 2 dog', 
       ['3110', '23', '444.4', '11', '2']),
      ('hello 12 hi 89', 
       ['12', '89']),
      ('4', 
       ['4']),
      ('I like 74,600 commas not,500', 
       ['74,600', '500']),
      ('I like bad math 1+2=.001', 
       ['1', '+2', '.001'])]

for s, r in ss:
    rr = re.findall("[-+]?[.]?[\d]+(?:,\d\d\d)*[\.]?\d*(?:[eE][-+]?\d+)?", s)
    if rr == r:
        print('GOOD')
    else:
        print('WRONG', rr, 'should be', r)

Taken from this.

Read only numbers from a string

3 Answers3