python 用递归实现 数字组成的str转int

代码如下

def strToInt(s):
    result =0
    if(len(s) == 1):
        return int(s)
    else:
        start = int(s[0:1])
        result = (result+start)*10+strToInt(s[1:])
        return result

print(strToInt('781'))

运行结果不如人意：151 ，应该是781呀
百思不得其解

def change(s):
    if len(s) == 1:
        return int(s)
    res = int(s[0]) * (10 ** (len(s)-1)) + change(s[1:])
  
    return res
change('781')

(result+start)*10
改为
(result+start*10）

def strToInt(s):
    bs = "1"
    bs_list = []
    res = 0
    for i in range(len(s)):
        t_bs = int(bs)
        bs_list.append(t_bs)
        bs += "0"
    n = 1
    for item in range(len(s)):
        ad = int(s[item]) * int(bs_list[-n])
        n += 1
        res += ad
    return res

print(strToInt('78111'))