encode-and-decode-strings.py

class Codec:
    def encode(self, strs):
        """Encodes a list of strings to a single string.
        
        :type strs: List[str]
        :rtype: str
        """
        return "".join("{}:{}".format(len(s), s) for s in strs)

    def decode(self, s):
        """Decodes a single string to a list of strings.
        
        :type s: str
        :rtype: List[str]
        """
        strs = []
        i = j = 0
        while i < len(s):
            j = s.find(":", i)
            i = j + int(s[i:j]) + 1
            strs.append(s[j + 1 : i])
        return strs


# Your Codec object will be instantiated and called as such:
# codec = Codec()
# codec.decode(codec.encode(strs))