Removing all non-numeric values from a string

Question

The task is to return all numbers in a string, excluding all letters. My current is such as:

def get_digits(cs: str) -> str:
   

    str1 = ''
    for c in cs:
        if c.isdigit():
            a = str1.join(c)

        

    return a

For example, when get_digits("a1b2c3") is entered, the desired output is 123. Currently the returned result is '3'. Any help would be much appreciated. Thank you

https://stackoverflow.com/questions/4289331/how-to-extract-numbers-from-a-string-in-python — Gedas Miksenas, Apr 07 '22 at 10:03
you have 2 way to do it ,1. save the digital char in a list then use join 2. concatenate string each time u find — WolfCode, Apr 07 '22 at 10:09

score 0 · Answer 1 · answered Apr 07 '22 at 10:08

Regex is your better option here, if you want to remove all non-digit, you can do something like

>>> cs = "a1b2c3"
>>> re.sub('\D', '', cs)
'123'

But you can do better by extracting directly numbers in a list

>>> cs = "a1b24c3"
>>> re.findall(r'\d+', cs)
['1', '24', '3']

both solutions works, it depends of your use case.

score 0 · Answer 2 · answered Apr 07 '22 at 10:10

Your code is returning '3' because you are overwriting the 'a' variable each time the iteration of the for loop ends You can just concatenate each result number to the str1 variable:

def get_digits(cs: str) -> str:
       

    str1 = ''
    for c in cs:
        if c.isdigit():
            str1 += c
            # str1 += c it's the same as str1 = str1 + c

        

    return str1

This will return your desired output

score 0 · Answer 3 · answered Apr 07 '22 at 10:40

0

You can achieve this by using only string related functions, like below:

input_str = "a1b2c3"

numbers = ''.join((ch if ch in '0123456789' else ' ') for ch in input_str)
numbers_list = [int(i) for i in numbers.split()]

print(numbers_list)

answered Apr 07 '22 at 10:40

Dan Constantinescu

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Removing all non-numeric values from a string

3 Answers3