sum of num in given string-CodePudding

given string = "12ab23cdef456gh789", sum the number, output should be 12 23 456 789 = 1280

my code:

s = "ab12cd23ed456gh789"
st = ''
for letter in s:
    if letter.isdigit():
        st  = letter
    else:
        if st[-1].isdigit():
            st  = ','
st = [int(letter) for letter in st.split(',')]
print(st)
print(sum(st))

error:

Traceback (most recent call last):
    if st[-1].isdigit():
IndexError: string index out of range

Process finished with exit code 1

not sure where i am going wrong, can someone please help me here?

CodePudding user response：

You can use a regular expression to extract all consecutive sequences of digits.

import re
string = "12ab23cdef456gh789"
res = sum(map(int, re.findall(r'\d ', string)))
print(res)

CodePudding user response：

The issue with your code is that for the first letter, st is empty and you're trying to get the last element, which does not exist. Just add a check to make sure st isn't empty like this:

s = "ab12cd23ed456gh789"
st = ''
for letter in s:
    if letter.isdigit():
        st  = letter
    else:
        if len(st) != 0 and st[-1].isdigit():
            st  = ','
st = [int(letter) for letter in st.split(',')]
print(st)
print(sum(st))

However, it is generally better to use a regular expression for this instead. I know this is probably a homework question so you can't use a regular expression, but here's how you'd do one anyway:

import re

s = "ab12cd23ed456gh789"
n = sum([int(match) for match in re.findall(r'\d ', s)])
print(n)