Defanging an IP Address — Python

# Time:  O(n)
# Space: O(1)

class Solution(object):
    def defangIPaddr(self, address):
        """
        :type address: str
        :rtype: str
        """
        result = []
        for c in address:
            if c == '.':
                result.append("[.]")
            else:
                result.append(c)
        return "".join(result)