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 booleannp.extract
is equivalent toarr[condition]
.Note that
place
does the exact opposite ofextract
.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.
Returns: 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])