Chapter 01

Meet the ndarray

Type some numbers

An ndarray (n-dimensional array) is NumPy’s container for numbers: a rectangular grid where every element has the same type.

Type numbers in the a = box. ArrayLab writes the matching np.array([...]) call (see “Code that ran” below) and real NumPy builds the array.

Remember: An ndarray is rectangular and holds one type of element.

a = dtype shape (2, 3)

Try

Spaces or commas between values · new line = new row · blank line = new 2-D layer (3-D array).

Starting Python… (first visit downloads ≈ 15 MB, then it is cached)

a.shape = ( 2 axis 0 rows,3 axis 1 columns )

Hover or focus a cell to see its index.

Every element has one index per axis — 2 numbers, because ndim is 2. The shape lists how long each axis is.

axis 0 has length 2: moving along it changes the 1st index — you step between rows.
axis 1 has length 3: moving along it changes the 2nd index — you step between columns.

Python not started

import numpy as np

a = np.array([[1, 2, 3],
              [4, 5, 6]])

a

Output

Output appears here.