Leetcode 804. Unique Morse Code Words

class Solution:
    def uniqueMorseRepresentations(self, words: List[str]) -> int:
        az = [chr(x) for x in range(ord('a'), ord('z') + 1)]
        morse = [".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."]
        mapping = {}
        for i in range(len(morse)):
            mapping[az[i]] = morse[i]

        result = set()
        for word in words:
            temp = ''
            for ch in word:
                temp = temp + mapping[ch]
            result.add(temp)

        return len(result)