Sword finger offer46 translates numbers into strings

Given a number , We translate it as a string according to the following rules ：0 Translate into “a” ,1 Translate into “b”,……,11 Translate into “l”,……,25 Translate into “z”. A number may have more than one translation . Please program a function , Used to calculate how many different translation methods a number has .

class Solution:
    def translateNum(self, num: int) -> int:
        s = str(num)
        a = b = 1
        for i in range(2, len(s) + 1):
            tmp = s[i - 2:i]
            c = a + b if "10" <= tmp <= "25" else a
            b = a
            a = c
        return a