500. Keyboard Row

class Solution(object):
    def findWords(self, words):
        """
        :type words: List[str]
        :rtype: List[str]
        """
        keyboard= ["qwertyuiop", "asdfghjkl", "zxcvbnm"]
        new_list=[]
        for a_word in words:
            lower_a_word = a_word.lower()
            for line in keyboard:
                if set(lower_a_word).issubset(set(line)):
                    new_list.append(a_word)
        return new_list
best solution

class Solution(object):
    def findWords(self, words):
        line1, line2, line3 = set('qwertyuiop'), set('asdfghjkl'), set('zxcvbnm')
        ret = []
        for word in words:
            w = set(word.lower())
            if w.issubset(line1) or w.issubset(line2) or w.issubset(line3):
                ret.append(word)
        return ret