Splitting a numpy array into two subsets of different sizes

Question

I have a numpy array of a shape (400, 3, 3, 3) and I want to split it into two parts, so I would get arrays like (100, 3, 3, 3) and (300, 3, 3, 3).

I was playing with numpy split methods, e.g.:

subsets = np.array_split(arr, 2)

which gives me what I want, but it divides the original array into two halves the same size and I don't know how to specify these sizes. It'd be probably easy with some indexing (I guess) but I'm not sure how to do it.

I'd use the slice notation like @cᴏʟᴅsᴘᴇᴇᴅ suggests, it potentially takes much less memory (since the arrays would share the underlying buffer). Not sure if that is what will happen with split, but if you must, you could do subsets = np.array_spit(arr, [100]) — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Nov 5, 2017 at 8:45
The slice notation is exactly what I was looking for, thanks. — T.Poe
– T.Poe, Commented Nov 5, 2017 at 8:48

cs95 · Accepted Answer · 2017-11-05 08:51:18Z

6

As mentioned in my comment, you can use the Ellipsis notation to specify all axes:

x, y = arr[:100, ...], arr[100:, ...]

answered Nov 5, 2017 at 8:51

cs95

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