What is the expected output of the following code? ``python 1 w = [7, 3, 23, 42] 2 x = w[1:] 3 y = w[1:] 4 z = w 5 y[0] = 10 6 z[1] = 20 7 print(w) ``

Question

1 w = [7, 3, 23, 42]
2 x = w[1:]
3 y = w[1:]
4 z = w
5 y[0] = 10
6 z[1] = 20
7 print(w)

Options

• A[7, 3, 23, 42]
• B[7, 20, 23, 42]
• C[10, 20, 23, 42]
• D[10, 20, 23, 42]

• A
  8% (3)
• B
  85% (34)
• C
  5% (2)
• D
  3% (1)

Explanation

B is correct because z = w creates an alias - both z and w point to the exact same list object in memory, so z[1] = 20 directly mutates w, changing index 1 from 3 to 20.

A is wrong because it ignores the aliasing on line 4; z[1] = 20 does change w, so the list cannot remain [7, 3, 23, 42].

C and D are identical and both wrong because y = w[1:] creates a brand-new list (a shallow copy of a slice), so y[0] = 10 only modifies y - w is completely unaffected by that assignment.

Memory tip: Think of = with a slice (w[1:]) as "cut and copy" - you get a fresh list. Think of = without a slice (z = w) as "copy the sticky note pointing to the same box" - both names refer to one object, so changes through either name affect the same underlying data.

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