numpy.extract — NumPy v2.2 Manual (original) (raw)

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:

conditionarray_like

An array whose nonzero or True entries indicate the elements of _arr_to extract.

arrarray_like

Input array of the same size as condition.

Returns:

extractndarray

Rank 1 array of values from arr where condition is True.

Examples

import numpy as np 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])