return if move sequences qualifies as a valid circle

JudgeRouteCircle.py

'''
Initially, there is a Robot at position (0, 0). Given a sequence of its
moves, judge if this robot makes a circle, which means it moves back to
the original place.

The move sequence is represented by a string. And each move is represent
by a character. The valid robot moves are R (Right), L (Left), U (Up) and
D (down). The output should be true or false representing whether the
robot makes a circle.

Example 1:
Input: "UD"
Output: true
Example 2:
Input: "LL"
Output: false

'''

class Solution:
    def judgeCircle(self, moves):
        initpos = [0,0]
        pos = [0,0]
   
        """
        :type moves: str
        :rtype: bool
        """
#         self.validMoves = {
#             'L' : 0,
#             'R' : 1,
#             'U' : 2,
#             'D' : 3
#         }
        for move in moves:
            if move is 'R':
                pos[0] += 1
            elif move is 'L':
                pos[0] -= 1
            elif move is 'U':
                pos[1] += 1
            else:
                pos[1] -= 1


        if pos == initpos:
            print("True")
            return True

        print("False")
        return False