- numpy.putmask(a, mask, values)¶
Changes elements of an array based on conditional and input values.
Sets a.flat[n] = values[n] for each n where mask.flat[n]==True.
If values is not the same size as a and mask then it will repeat. This gives behavior different from a[mask] = values.
The putmask functionality is also provided by copyto, which can be significantly faster and in addition is NA-aware (preservena keyword). Replacing putmask with np.copyto(a, values, where=mask) is recommended.
a : array_like
mask : array_like
Boolean mask array. It has to be the same shape as a.
values : array_like
Values to put into a where mask is True. If values is smaller than a it will be repeated.
>>> x = np.arange(6).reshape(2, 3) >>> np.putmask(x, x>2, x**2) >>> x array([[ 0, 1, 2], [ 9, 16, 25]])
If values is smaller than a it is repeated:
>>> x = np.arange(5) >>> np.putmask(x, x>1, [-33, -44]) >>> x array([ 0, 1, -33, -44, -33])