#### Previous topic

numpy.searchsorted

#### Next topic

numpy.count_nonzero

# numpy.extract¶

numpy.extract(condition, arr)[source]

Return the elements of an array that satisfy some condition.

This is equivalent to np.compress(ravel(condition), ravel(arr)). If condition is boolean np.extract is equivalent to arr[condition].

Note that place does the exact opposite of extract.

Parameters: condition : array_like An array whose nonzero or True entries indicate the elements of arr to extract. arr : array_like Input array of the same size as condition. extract : ndarray Rank 1 array of values from arr where condition is True.

Examples

>>> arr = np.arange(12).reshape((3, 4))
>>> arr
array([[ 0,  1,  2,  3],
[ 4,  5,  6,  7],
[ 8,  9, 10, 11]])
>>> condition = np.mod(arr, 3)==0
>>> condition
array([[ True, False, False,  True],
[False, False,  True, False],
[False,  True, False, False]])
>>> np.extract(condition, arr)
array([0, 3, 6, 9])

If condition is boolean:

>>> arr[condition]
array([0, 3, 6, 9])