Leetcode: Unique Paths II @Python

class Solution:
    # @param obstacleGrid, a list of lists of integers
    # @return an integer
    def uniquePathsWithObstacles(self, obstacleGrid):
        row=len(obstacleGrid)
        col=len(obstacleGrid[0])
        if row*col==0:
            return 1
        dp=[[0 for i in range(col)] for j in range(row)]
        for i in range(row):
            if obstacleGrid[i][0]==0:
                dp[i][0]=1
            else:
                break
        for j in range(col):
            if obstacleGrid[0][j]==0:
                dp[0][j]=1
            else:
                break
        for i in range(1,row):
            for j in range(1,col):
                if obstacleGrid[i][j]==1:
                    dp[i][j]=0
                else:
                    dp[i][j]=dp[i-1][j]+dp[i][j-1]
        return dp[row-1][col-1]