all Python 3Built-in typesterm

slice

slices

The built-in slice object type: slice(start, stop, step), created by a[start:stop:step].

Syntax

slice(start, stop, step)

You rarely build a slice by hand: it pays off when the same slice is reused under a name in several places, or when you write your own __getitem__ and need to tell an integer index from a slice object. As with range, a single argument is stop, not start: slice(5) means start=None, stop=5. To resolve it against a concrete length use indices(): s.indices(len(seq)) returns a ready triple with None and negative values already sorted out.

Examples

s = slice(1, 5, 2)
print((s.start, s.stop, s.step))   # → (1, 5, 2)
print('abcdefgh'[s])   # → bd
print([0, 1, 2, 3, 4][slice(2, 4)])   # → [2, 3]
print('abcdef'[slice(None, None, -1)])   # → fedcba
print(slice(5).indices(3))   # → (0, 3, 1)

See also

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