Chapter 03

Axis

Axis 0

np.sum(a, axis=0) adds up values along axis 0: it walks down the first index while the other indices stay fixed.

For a 2-D array that means each column is summed. The arrows show the direction of collapse; cells with the same label end up in the same result element. Hover a result to see its sum.

Try this

Remember: axis=0 collapses the first axis; it disappears from the shape: (2, 3) → (3,).

a = dtype shape (2, 3)

Try

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

Function

axis

keepdims=True

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import numpy as np

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

result = np.sum(a, axis=0)
result

Output

Output appears here.