Leetcode: Sort Colors @Python

class Solution:
    # @param A a list of integers
    # @return nothing, sort in place
    def sortColors(self, A):
        n=len(A)
        p0,p2=0,n-1
        i=0
        while i<=p2:
            if A[i]==0:# swap 0 to p0
                A[p0],A[i]=A[i],A[p0]
                p0+=1
                i+=1
            elif A[i]==2:#swap 2 to p2
                A[p2],A[i]=A[i],A[p2]
                p2-=1
            else:
                i+=1