access
list[i] / list[i:j:k]
Subscript syntax to read a single element (by index) or a new list (by slice). Slicing always returns a new shallow copy; out-of-range slice bounds are silently clamped while single-index access raises IndexError.
list[index] | list[start:stop:step]Parameters
| Parameter | Purpose |
|---|---|
| index | Single int; negative counts from the end. Out of range raises IndexError. |
| start:stop | Half-open range [start, stop); missing bounds default to 0 and len(list). |
| step | Stride; negative reverses (e.g. lst[::-1] is a reversed copy). |
Examples
>>> lst = [10, 20, 30, 40]
>>> lst[1]
20
>>> lst[-1]
40Negative indices count from the right.
>>> lst = [1, 2, 3, 4, 5]
>>> lst[1:4]
[2, 3, 4]Slice returns a new list.
>>> lst = [1, 2, 3]
>>> lst[::-1]
[3, 2, 1]Negative step reverses; a common idiom.
>>> lst = [1, 2, 3]
>>> lst[9]
IndexError: list index out of range
>>> lst[9:99]
[]Single-index raises; slice bounds silently clamp.
Gotcha
Slicing produces a SHALLOW copy — nested objects are shared. lst[9] raises IndexError but lst[9:99] returns [] silently.
Related methods
list.copy
Returns a shallow copy of the list — a new list containing the same element references. Equivalent to lst[:] or list(lst); does not recursively copy nested mutables.
list.reverse
Reverses the elements of the list in place. Returns None; O(n) time and O(1) extra space.
list.index
Returns the zero-based index of the first item equal to x within the optional [start, end) range. Raises ValueError if no match is found.
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