참고해보세요.

a = 'A5B100'
b = int(a.split('B')[0].split('A')[1])
c = int(a.split('B')[1])

아마 이런 걸 원했을 것 같은데요. isalpha , isnumeric 같은 스트링함수가 있습니다.

대충 짰습니다. 참고하세요.

>>> def get_str_count_pair(s: str):
    s1 = ''
    for i, c in enumerate(s):
        if c.isalpha():
            s1 += c
        else:
            s = s[i:]
            break
    print(s1, s)
    n1 = ''
    for i, c in enumerate(s):
        if c.isnumeric():
            n1 += c
        else:
            s = s[i:]
            break
    s2 = ''
    for i, c in enumerate(s):
        if c.isalpha():
            s2 += c
        else:
            s = s[i:]
            break
    print(s2, s)
    n2 = ''
    for i, c in enumerate(s):
        if c.isnumeric():
            n2 += c
        else:
            s = s[i:]
            break
    return s1 *(int(n1)) + s2*(int(n2))

>>> get_str_count_pair("A5B10")
A 5B10
B 10
'AAAAABBBBBBBBBB'
>>> get_str_count_pair("AX3B7")
AX 3B7
B 7
'AXAXAXBBBBBBB'