get occurrences of a list in an array - python

Question

a = np.array([1,2,4,2,3,4,1])
s = [1,2]

How can I get an array which tells me whether the elements in s exist in a? This is what I'm hoping to get:

[True, True, False, True, False, False, True]

rafaelc · Accepted Answer · 2019-05-06 02:56:13Z

5

>>> np.isin(a,s)

array([ True,  True, False,  True, False, False,  True])

answered May 6, 2019 at 2:56

community wiki

Sign up to request clarification or add additional context in comments.

Comments

Zik · Accepted Answer · 2019-05-06 02:56:46Z

0

no numpy, you can do like this

a = [1,2,4,2,3,4,1]
s = [1,2]
t = list(map(lambda a: a in s, a))

if is s is larger, set is more effective

 a = [1,2,4,2,3,4,1]
 s = set([1,2])
 t = list(map(lambda a: a in s, a))

answered May 6, 2019 at 2:55

Zik

3023 silver badges11 bronze badges

This is way slower than np.isin

MarredCheese · Accepted Answer · 2019-05-06 03:39:54Z

0

import numpy as np

a = np.array([1, 2, 4, 2, 3, 4, 1])
s = [1, 2]
r = [n in s for n in a]
print(r)  # [True, True, False, True, False, False, True]

MarredCheese

21.3k12 gold badges109 silver badges105 bronze badges

answered May 6, 2019 at 2:55

mahadev

11 bronze badge