How can the different elements of the list be multiplied (str and int)?

Question

I am trying to get conversion of string like 'a3b4' to 'aaabbbb'. How can this be done without additional modules? So far my code looks like this:

s = 'a3b4'
n = ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
a = []
b = []

for i in range(len(s)):
    if s[i] in n:
        a.append(s[i])
    if s[i] not in n:
        b.append(s[i])
for i in range(len(b)):
    print(b[i])

Answer 1

This should work:

letters = list(s[::2])
nums = list(s[1::2])
res = ''.join([a*int(b) for a,b in zip(letters,nums)])

>>res
Out[1]: 'aaabbbb'

EDIT:

If you want to match any srting and any digits you should use regex:

letters = re.findall(r'[a-z]+',s)
nums = re.findall(r'\d+',s)
res = ''.join([a*int(b) for a,b in zip(letters,nums)])

for:

 s='a10b3'

output is:

>>res
Out[2]: 'aaaaaaaaaabbb'