Python和numpy - 将数组中的多个值转换为二进制

Question

我有一个相当大的numpy数组,大约1mill.不同数量的数字约为8,编号为1-8.

假设我想给出数字2,我想将所有2的重新编码为1,其余的重新编号为0.

i.e. 
2==>1
1345678==0

Is there a pythonic way to do this with numpy?


[1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8]=> [0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0]

谢谢

Answer 1

这a == 2是NumPy数组的结果a:

>>> a = numpy.random.randint(1, 9, size=20)
>>> a
array([4, 5, 1, 2, 5, 7, 2, 5, 8, 2, 4, 6, 6, 1, 8, 7, 1, 7, 8, 7])
>>> a == 2
array([False, False, False,  True, False, False,  True, False, False,
        True, False, False, False, False, False, False, False, False,
       False, False], dtype=bool)
>>> (a == 2).astype(int)
array([0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])

如果您想要进行更改a,最有效的方法是使用numpy.equal():

>>> numpy.equal(a, 2, out=a)
array([0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])