python数组切片范围[：，：]

Question

I'm testing a array slicing there is a problem.

I want to print (1,1)~(3,3) values, however python prints (1,1)~(2,2) why?

import numpy as np
a = np.reshape(np.arange(25), (5,5))
print(a[1:3, 1:3])

Answer 1

Because 3 in your example is exclusive. Use 4 instead:

print(a[1:4, 1:4])

When using Python's start:stop:step slice notation, start is inclusive, but stop is not.