[英]how to find all the index of an element in a list Python
如果我有清单
a=[1,0,0,1,0,1,1,1,0,1,0,0]
我想分别找到索引0和1,在这种情况下,
index_0 = [1,2,4,8,10,11]
index_1 = [0,3,5,6,7,9]
有没有一种有效的方法可以做到这一点?
index_0 = [i for i, v in enumerate(a) if v == 0]
index_1 = [i for i, v in enumerate(a) if v == 1]
或使用numpy:
import numpy as np
a = np.array(a)
index_0 = np.where(a == 0)[0]
index_1 = np.where(a == 1)[0]
使用itertools.compress
:
>>> a=[1,0,0,1,0,1,1,1,0,1,0,0]
>>> index_1 = [x for x in itertools.compress(range(len(a)),a)]
>>> index_1
[0, 3, 5, 6, 7, 9]
>>> index_0 = [x for x in itertools.compress(range(len(a)),map(lambda x:not x,a))]
>>> index_0
[1, 2, 4, 8, 10, 11]
您可以使用一个for循环来实现:更高更好的效率
>>> a=[1,0,0,1,0,1,1,1,0,1,0,0]
>>> index_0 = []
>>> index_1 = []
>>> for i,x in enumerate(a):
... if x: index_1.append(i)
... else: index_0.append(i)
...
>>> index_0
[1, 2, 4, 8, 10, 11]
>>> index_1
[0, 3, 5, 6, 7, 9]
另一种方法是:
import os
a = [1,0,0,1,0,1,1,1,0,1,0,0]
index_0 = []
index_1 = []
aux = 0
for i in a:
if i == 0:
index_0.append(aux)
aux += 1
else:
index_1.append(aux)
aux += 1
print index_0
print index_1
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