python regex for substring list of number

Question

Giving this string:

numbers 1 2 10 20

where the amount of numbers might be 1 or more, how can I get only the numbers? (i.e expression that would return:

[1, 2, 10, 20]

My closest try was:

re.findall(r'numbers (\d +)', 'numbers 1 2 10 20')
>>> ['1 ']

Edit:

The case above is not telling the whole story so I will explain a bit more.

I have a list of strings, and I need to first figure out whether one of them is matching the pattern number X Y Z as explained above. If such a string is indeed in that list I want to extract from it only the numbers.

I can do it in multiple steps but I wonder If I can use regex here to get what I want with a one-liner.

Examples:

Let's assum that the function func1(list) is our magic function that do all I requires.

l1 = ['letters a b c', 'numbers 1 12 6']
l2 = ['animalas dog cat', 'colors red blue']

>>> func1(l1)
OUT: [1, 12, 6]

>>> func2(l1)
OUT: []

`print(re.findall(r"(\d+)", "numbers 1 2 10 20"))` ? – Rakesh Jan 22 '19 at 11:50 — Rakesh, Jan 22 '19 at 11:50

score -1 · Accepted Answer · edited Jun 20 '20 at 09:12

-1

strr = "numbers 1 2 10 20"

Uhm:

print(''.join([n for n in strr if n.isdigit()]))

OR

print([int(s) for s in re.findall(r'\b\d+\b', strr)])

OR

import re
print(map(int, re.findall('\d+', strr)))

OUTPUT:

[1, 2, 10, 20]

Based on OP's EDIT:

You need to match the string first before you fetch all the digits out of it:

if re.match("numbers .*"+ r'\b\d+\b', strr):
    print("String pattern matched, Now extracting..")

Hence:

import re

def func1(strrList):
        for strr in strrList:        
            if re.match("numbers .*"+ r'\b\d+\b', strr):
                print("String pattern matched, Now extracting..")
                print(map(int, re.findall('\d+', strr)))
            else:
                print("String pattern failed to match.")


l1 = ['letters a b c', 'numbers 1 12 6']
l2 = ['animalas dog cat', 'colors red blue']

func1(l1)

OUTPUT:

String pattern failed to match.

String pattern matched, Now extracting..

[1, 12, 6]

edited Jun 20 '20 at 09:12

Community

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answered Jan 22 '19 at 11:50

DirtyBit

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Please see my edit, the `numbers` prefix is important to the issue i am facing. – Andy Thomas Jan 22 '19 at 12:00
@AndyThomas Could you provide a elaborated example? Perhaps with a sample I/O? – DirtyBit Jan 22 '19 at 12:00
I have added I/O exmple. – Andy Thomas Jan 22 '19 at 12:07
@AndyThomas edited! – DirtyBit Jan 22 '19 at 12:10
Thank you, this is of course will do the trick. However I hoped that there is a way to catch the `numbers` prefix and extract only the numbers after it. From your answer I conclude that there isn't. Right? – Andy Thomas Jan 22 '19 at 12:15
@AndyThomas added the complete example. – DirtyBit Jan 22 '19 at 12:19
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I am accepting your answer because as I said it is matching my requirements but I am still hoping to find out about a one-liner call for this issue :) Thank you. – Andy Thomas Jan 22 '19 at 12:25

python regex for substring list of number

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