Check for array - is value contained in another array?

Question

I'd like to return a boolean for each value in array A that indicates whether it's in array B. This should be a standard procedure I guess, but I can't find any information on how to do it. My attempt is below:

A = ['User0','User1','User2','User3','User4','User0','User1','User2','User3'
     'User4','User0','User1','User2','User3','User4','User0','User1','User2'
     'User3','User4','User0','User1','User2','User3','User4','User0','User1'
     'User2','User3','User4','User0','User1']
B = ['User3', 'User2', 'User4']
contained = (A in B)

However, I get the error:

ValueError: shape mismatch: objects cannot be broadcast to a single shape

I'm using numpy so any solution using numpy or standard Python would be preferred.

Divakar · Accepted Answer · 2015-04-04 22:21:05Z

21

You can use in1d I believe -

np.in1d(A,B)

answered Apr 4, 2015 at 22:21

Divakar

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Selcuk · Accepted Answer · 2015-04-04 22:21:19Z

6

For testing it without using numpy, try:

contained = [a in B for a in A]

result:

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

edited Apr 4, 2015 at 22:21

answered Apr 4, 2015 at 22:18

Selcuk

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1 Comment

hpaulj Over a year ago

For this small example, this list comprehension is considerably faster than np.in1d.

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