CODEWITHSUNDEEP
pythonnumpy
Baktaawar
Baktaawar

Reputation: 7490

Getting index of an array value

I have two arrays as follows: 

e = np.array([True, False, True, True])    
f = np.array([True, False, False, True])

I want to get the index i where e[i] and f[i] == True.

The expected output for the above will be:

[0,3] since e[0] == True and f[0] == True; e[3] and f[3] ==True

There may be more of such matches, so I need a list of all of the indices which satisfy the above condition.

I tried to find the list of matching values by doing this: 

list(e&f)
Out[474]:
[True, False, False, True]

To get the index, I thought I could use .index(True) of list. But it doesn't work or just gives output as 0. Maybe only giving the first index and not all.

Finally, I need the 1 added to each element of output so instead of [0,3] output should be [1,4] but this is easy I can do that if I get the indices,

Upvotes: 0

Views: 77

Answers (4)

GreatSUN
GreatSUN

Reputation: 50

Something else if you don't want to be dependent on numpy:

e=[True, False, True, True]
f=[True, False, False, True]

for idx, val in enumerate(e):
  if cmp(e[idx], f[idx]) is 0:
    print idx+1, val

Upvotes: 1

user3404344
user3404344

Reputation: 1727

or simply this 

np.where(e&f)

Upvotes: 1

michael_j_ward
michael_j_ward

Reputation: 4559

Take a look at numpy.where in the docs

np.where(e&f)[0]

Outputs:

 array([0, 3])

Upvotes: 3

mhawke
mhawke

Reputation: 87064

You can just use a list comprehension to pick them out:

>>> e = np.array([True, False, True, True])    
>>> f = np.array([True, False, False, True])
>>> [i for i,v in enumerate(e&f, 1) if v]
[1, 4]

Using enumerate() you can specify the initial index, in this case 1.

Upvotes: 1

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