python - Numpy slicing from variable

Question

I'm trying to slice a numpy array using a slice that is predefined in a variable. This works:

b = fromfunction(lambda x,y: 10*x+y, (5,4),dtype=int) # Just some matrix

b[1:3,1:3]
# Output:
# array([[11, 12],
#       [21, 22]])

But what I want to do is somthing like this:

slice = "1:3,1:3"
b[slice]
# Output:
# array([[11, 12],
#       [21, 22]])

It is not important to me what type the slice-variable has, I'm just using a string as an example. How do I save a slice-specifier like that?

Answer 1

You can use the built-in slice function

s = slice(1,3)
b[s,s]

ds = (s,s)
b[ds]