Views and copies in Python

Slicing gives a view; forgetting that is how numpy surprises people.

import numpy as np

original = np.arange(6)
view = original[2:5]
clone = original[2:5].copy()

view[0] = 99
clone[1] = -1

print(original)
print(view.base is original, clone.base is None)
print(np.shares_memory(original, view),
      np.shares_memory(original, clone))

How it works

1. A basic slice shares memory with the original.
2. copy() breaks the link deliberately.
3. base tells you whether an array owns its data.

Keywords and builtins used here

• as
• print

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Step 2 of 4 in Maths & memory, step 17 of 22 in NumPy.

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