copy

`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.

Syntax

list.copy()

Parameters

Parameter	Purpose
(no args)	copy() takes no arguments.
shallow only	For nested lists/dicts, use copy.deepcopy() to duplicate the inner objects too.

Examples

>>> a = [1, 2, 3]
>>> b = a.copy()
>>> b.append(4)
>>> a
[1, 2, 3]

Independent top-level lists.

>>> a = [[1, 2], [3]]
>>> b = a.copy()
>>> b[0].append(99)
>>> a
[[1, 2, 99], [3]]

Shallow — the inner list is shared between a and b.

>>> import copy
>>> b = copy.deepcopy(a)

deepcopy fully clones nested structures.

>>> a = [1, 2]; b = a[:]
>>> b is a
False

lst[:] and list(lst) are the classical shallow-copy idioms.

Gotcha

It is a SHALLOW copy — nested mutables (lists, dicts, objects) are still shared with the original. Use copy.deepcopy for a fully independent tree.

Related methods

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.extend

Extends the list by appending every element from an iterable, in order. Mutates in place and returns None; equivalent to `list += iterable`.

sorted (built-in)

Built-in function that returns a NEW sorted list from any iterable, leaving the source untouched. Uses the same stable Timsort and key/reverse arguments as list.sort.

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