class Solution:
    # @param    A       a list of integers
    # @param    elem    an integer, value need to be removed
    # @return an integer
    def removeElement(self, A, elem):
        while elem in A: A.remove(elem)
        return len(A)

快一点的做法是不删除元素

class Solution:
    # @param    A       a list of integers
    # @param    elem    an integer, value need to be removed
    # @return an integer
    def removeElement(self, A, elem):
        k = 0
        for i in A:
            if i != elem:
                A[k] = i
                k += 1
        return k