没有用到map和reduce但是也实现了，求助哪些部分可以用map和reduce替

    n = len(s)
    a = -1
    for i in range(n):
        a += 1
        if s[i] == '.':
            break
    s1 = ''
    s2 = ''
    for i in range(a):
        s1 = s1 + s[i]
    for i in range(n-a-1):
        s2 = s2 + s[i+a+1]
    S = float(s1 +'.'+ s2)
    return S