numpy.where() in Python
The numpy.where() function returns the indices of elements in an input array where the given condition is satisfied.
Syntax : numpy.where(condition[, x, y])
Parameters:
condition : When True, yield x, otherwise yield y.
x, y : Values from which to choose. x, y and condition need to be broadcastable to some shape.Returns:
out : [ndarray or tuple of ndarrays] If both x and y are specified, the output array contains elements of x where condition is True, and elements from y elsewhere.If only condition is given, return the tuple condition.nonzero(), the indices where condition is True.
Code #1:
# Python program explaining
# where() function
import
numpy as np
np.where([[
True
,
False
], [
True
,
True
]],
[[
1
,
2
], [
3
,
4
]], [[
5
,
6
], [
7
,
8
]])
|
Output :
array([[1, 6],
[3, 4]])
Code #2:
# Python program explaining
# where() function
import
numpy as np
# a is an array of integers.
a
=
np.array([[
1
,
2
,
3
], [
4
,
5
,
6
]])
print
(a)
print
(
'Indices of elements <4'
)
b
=
np.where(a<
4
)
print
(b)
print
(
"Elements which are <4"
)
print
(a[b])
|
Output :
[[1 2 3] [4 5 6]] Indices of elements <4 (array([0, 0, 0], dtype=int64), array([0, 1, 2], dtype=int64)) Elements which are <4 array([1, 2, 3])
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