python删除数组中元素

有数组a，要求去掉a所有为0的元素

a = [2,4,0,8,9,10,100,0,9,7]

1. Filter
   a= filter(None, a)

2. Lambada
   a = filter(lambda x: x != 0, a)

3. for
   for b in a:
   if b == 0:
   a.remove(b)