Python - find digits in a string

Question

def get_digits(str1):
    c = ""

    for i in str1:
        if i.isdigit():
            c += i
            return c

Above is the code that I used and the problem is that it only returns only the first digit of strings. For this, I have to keep both for loop and return statement. Anyone knows how to fix?

Thanks.

Answer 1

As the others said, you have a semantic problem on your indentation, but you don't have to write such function to do that, a more pythonic way to do that is:

def get_digits(text):
    return filter(str.isdigit, text)

On the interpreter:

>>> filter(str.isdigit, "lol123")
'123'

Some advice

Always test things yourself when people shows 'faster' methods:

from timeit import Timer

def get_digits1(text):
    c = ""
    for i in text:
        if i.isdigit():
            c += i
    return c

def get_digits2(text):
    return filter(str.isdigit, text)

def get_digits3(text):
    return ''.join(c for c in text if c.isdigit())

if __name__ == '__main__':
    count = 5000000
    t = Timer("get_digits1('abcdef123456789ghijklmnopq123456789')", "from __main__ import get_digits1")
    print t.timeit(number=count)

    t = Timer("get_digits2('abcdef123456789ghijklmnopq123456789')", "from __main__ import get_digits2")
    print t.timeit(number=count)

    t = Timer("get_digits3('abcdef123456789ghijklmnopq123456789')", "from __main__ import get_digits3")
    print t.timeit(number=count)



~# python tit.py
19.990989106  # Your original solution
16.7035926379 # My solution
24.8638381019 # Accepted solution

Answer 2

Your indentation is a bit borked (indentation in Python is quite important). Better:

def get_digits(str1):
    c = ""
    for i in str1:
        if i.isdigit():
            c += i
    return c

A shorter and faster solution using generator expressions:

''.join(c for c in my_string if c.isdigit())