In regular python array, a slice view of an array is actually a copy. Modifiying elements through the slice won't affect the original array.
>>> arr = [0, 1, 2]
>>> arr[0:][0] = 100
>>> arr
[0, 1, 2]
However, with numpy, the slice view of the array won't create a extra copy. And thus, modifying the elements through the slice will change the original data.
>>> import numpy as np
>>> arr = np.array([0, 1, 2])
>>> arr[0:][0] = 100
>>> arr
array([100, 1, 2])