Sorting along axes in NumPy - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does sorting along an axis mean in a NumPy array?

Sorting along an axis means arranging the elements in order (usually ascending) along a specific dimension (row or column) of a NumPy array, without changing the other dimensions.

beginner

How do you sort a 2D NumPy array along rows?

Use np.sort(array, axis=1). This sorts each row independently, arranging elements in ascending order within each row.

intermediate

What is the default axis used by np.sort() if none is specified?

The default axis is -1, which means sorting is done along the last axis of the array.

intermediate

How does sorting along axis=0 differ from axis=1 in a 2D array?

Sorting along axis=0 sorts each column independently (top to bottom), while axis=1 sorts each row independently (left to right).

advanced

Can you sort a 3D NumPy array along a specific axis? How?

Yes. Use np.sort(array, axis=n) where n is 0, 1, or 2. This sorts elements along that axis while keeping other axes intact.

What does np.sort(arr, axis=0) do on a 2D array?

A Sorts each row independently

B Sorts each column independently

C Sorts the entire array as a flat list

D Does not sort anything

Sorting with axis=0 sorts elements down each column independently.

If you want to sort each row of a 2D array, which axis should you use?

A axis=0

B axis=None

C axis=-1

D axis=1

axis=1 sorts along rows, sorting elements within each row.

What is the default axis for np.sort() if you don't specify it?

A axis=0

B axis=1

C axis=-1 (last axis)

D axis=None (flattened)

By default, np.sort sorts along the last axis (axis=-1).

Which function would you use to sort a NumPy array in-place along an axis?

A array.sort()

B np.argsort()

C np.sorted()

D np.sort()

array.sort() sorts the array in-place along the specified axis.

Sorting a 3D array along axis=2 means sorting along which dimension?

A The third dimension

B The second dimension

C The first dimension

D The flattened array

Axis=2 refers to the third dimension in a 3D array.

Explain how sorting along different axes affects a 2D NumPy array.

Think about rows vs columns and how sorting changes their order.

Describe how to sort a 3D NumPy array along a specific axis and why this might be useful.

Consider how multi-dimensional data can be organized slice by slice.