Tuple Unpacking

Tuple unpacking (also called destructuring) assigns each element of a tuple to a separate variable in one statement.

Basic Unpacking

Try it live and unpack a tuple of your own:

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>>> point = (3, 7)
>>> x, y = point
>>> print(x, y)
3 7

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The number of variables on the left must match the number of elements in the tuple (or you get a ValueError).

Swapping Variables

The cleanest way to swap two variables in Python uses tuple unpacking. Try it live:

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>>> a, b = 10, 20
>>> a, b = b, a
>>> print(a, b)
20 10

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Python evaluates the right-hand side completely before assigning, so no temporary variable is needed.

Unpacking Function Return Values

A function can return multiple values as a tuple, and the caller can unpack them. Try it live and pass a different list:

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>>> def min_max(nums: list) -> tuple:
...     return min(nums), max(nums)
...
>>> lo, hi = min_max([3, 1, 4, 1, 5, 9])
>>> print(lo, hi)
1 9

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Unpacking in for Loops with zip()

zip(a, b) pairs up elements from two sequences. Unpacking in the for heading processes both at once. Try it live and edit the lists:

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>>> names = ["Alice", "Bob", "Carol"]
>>> scores = [88, 73, 95]
>>> for name, score in zip(names, scores):
...     print(f"{name}: {score}")
...
Alice: 88
Bob: 73
Carol: 95

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zip() stops at the shortest sequence. Use zip(strict=True) in Python 3.10+ to raise an error if the sequences have different lengths.

Extended Unpacking

A * prefix captures the “rest” of the sequence into a list. Try it live and move the * to a different position:

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>>> first, *rest = [1, 2, 3, 4, 5]
>>> print(first)   # 1
1
>>> print(rest)    # [2, 3, 4, 5]
[2, 3, 4, 5]
>>> *body, last = [1, 2, 3, 4, 5]
>>> print(body)    # [1, 2, 3, 4]
[1, 2, 3, 4]
>>> print(last)    # 5
5

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Experiment with unpacking below — try changing the number of variables on the left and watch when Python raises a ValueError:

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>>> a, b = 10, 20
>>> a, b = b, a          # swap, no temporary needed
>>> print("swapped:", a, b)
swapped: 20 10
>>> names = ["Alice", "Bob", "Carol"]
>>> scores = [88, 73, 95]
>>> for name, score in zip(names, scores):
...     print(f"{name}: {score}")
...
Alice: 88
Bob: 73
Carol: 95
>>> first, *rest = [1, 2, 3, 4, 5]
>>> print("first:", first, " rest:", rest)
first: 1  rest: [2, 3, 4, 5]

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