python 定义问题~~~!!!!!!!!!!!!!(希望用简单易懂的方法)

def countDigitsFromPosUntilLetter(st, pos):
    ret=0
    try:
        st=st[pos:]                
    except:
        return 0
    for i in st:
        if i.isdigit():
            ret+=1
        else:
            break
    return ret

 这个确实错了，应该只有在遇到letter或结尾才break，else换成elif i.isalpha()

def countDigitsFromPosUntilLetter(st, pos):
abs_len = len(st)
cnt = 0
if pos >= 0: #the pos can be both negative or positive.
if pos >= abs_len:
raise IndexError
elif abs(pos) > abs_len:
raise IndexError

if st:
for i in st[pos:]:
if i.isalpha():
break
if i.isdigit():
cnt += 1
return cnt

print(countDigitsFromPosUntilLetter('12abc!#456', 0))
print(countDigitsFromPosUntilLetter('12abc!#456', 1))
print(countDigitsFromPosUntilLetter('12abc!#456', 2))
print(countDigitsFromPosUntilLetter('12abc!#456', 0))

从所给的位置（pos)开始数字符串st中有多少个数字，直到遇到字母或者数到字符串尾为止，返回数到的数字个数。字符串可以包含字母，数字和特殊字符