# Indexing ndarray with unknown number of dimensions with range dynamically

## Question:

I have `data`

array with unknown shape and array `bounds`

of bounds for slicing `data`

. This code is for 3D `data`

, but is there any way of generalizing this to N-dim?

```
for b in bounds:
l0, u0 = b[0]
l1, u1 = b[1]
l2, u2 = b[2]
a = data[l0:u0, l1:u1, l2:u2]
print(a)
```

Tried using range python object as index, did not work.

Examples for data:

```
data2D = np.arange(2*3).reshape((2, 3))
data3D = np.arange(2*3*4).reshape((2, 3, 4))
```

Corresponding bounds:

```
bounds2D = np.array([[[0, 2], [0, 2]], [[0, 2], [1, 3]]])
bounds3D = np.array(
[
[[0, 2], [0, 2], [0, 2]],
[[0, 2], [0, 2], [2, 4]],
[[0, 2], [1, 3], [0, 2]],
[[0, 2], [1, 3], [2, 4]],
],
)
```

## Answers:

You can use the slice function to create a single slice from each element in `bounds`

. Then collect these slices into a single tuple and use it to correctly recover the wanted items of the array. You can adapt your code as follows:

```
import numpy as np
# The dimension of the slices is equal to the
# one specified by the bounds provided
def create_slices(bounds):
slices = list()
# Take a single item of the bounds and create corresponding slices
for b in bounds:
# Slices are collected inside a single tuple
slices.append(tuple([slice(l, u) for l, u in b]))
return slices
# 4D example data
data4D = np.arange(2*3*4*5).reshape((2,3,4,5))
# Bounds array for 4D data
bounds4D = np.array(
[
[[0, 2], [0, 2], [0, 2], [0, 2]],
[[0, 2], [0, 2], [0, 2], [2, 4]],
[[0, 2], [1, 3], [2, 4], [0, 2]],
[[0, 2], [1, 3], [2, 4], [2, 4]],
],
)
slices = create_slices(bounds4D)
# Each element of slices is a single slice that can be used on
# the corresponding data array
for single_slice in slices:
a = data4D[single_slice]
print("Slice", a)
```