I have a program that retrieves image and return the RGB image as 3D np.ndarray. I want to return np.ndarray([[[]]]) when image is not available.
Can we do it?
3 Answers
Use numpy.empty
Which returns a new array of given shape and type, without initializing entries.
import numpy as np
empty_array = np.empty((1, 1, 1))
empty_array
array([[[5.e-324]]])
OR
import numpy as np
empty_array = np.empty((1, 1, 0))
empty_array
array([], shape=(1, 1, 0), dtype=float64)
which is basically
np.array([[[]]])
DOCS for more help
1 Comment
bers
The second part nails it. The first half is irrelevant to the question.
simply return np.empty((10,10,10),object) because x=np.empty((10,10,10)) returns array with random values already stored in the memory buffer . x=np.empty((10,10,10),object) will return array with none values.
Here (10,10,10) dimension is just for example. Use the dimensions favourable for you.
1 Comment
Cshitiz Dhingra
np.full(shape=(1,1,1),fill_value=None) is also a good alternative to get array with none valuesIt's easy to make such an array:
In [128]: arr = np.array([[[]]])
In [129]: arr
Out[129]: array([], shape=(1, 1, 0), dtype=float64)
You could also use np.zeros((1,1,0)) (or empty); but it's no easier than [128].
But how are you going to use or test this? I suppose you could check:
In [130]: arr.nbytes
Out[130]: 0
I believe one of the image packages (cv2?) returns None if it can't load the image. Testing for None is easy, reliable, and widely used in python.
In [131]: arr = None
In [132]: arr is None
Out[132]: True
It might make more sent to use a 'image' with 0 size, but still the full 3 color channels, np.zeros((0,0,3), np.int8).
np.array([])return np.array([[[]]])