What is tuple unpacking and extended unpacking in Python?

Unpacking assigns the individual elements of a sequence to multiple variables in a single statement. The left side must have the same number of names as the sequence has elements, or you get a ValueError.

# Basic unpacking
x, y, z = (10, 20, 30)
first, second = 'AB'

# Swap without a temp variable
a, b = 1, 2
a, b = b, a
print(a, b)  # 2 1

# Unpacking a function return value
def min_max(nums):
    return min(nums), max(nums)

lo, hi = min_max([5, 2, 8, 1])
print(lo, hi)  # 1 8

Extended unpacking (Python 3+) uses the starred expression *rest to collect everything that does not fit into the explicit names:

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

# Useful for parsing structured payloads
header, *records = open('data.csv').readlines()

# Discard parts you don't need with _
_, important, _ = ('ignore', 'keep this', 'ignore')

Unpacking works on any iterable — lists, tuples, strings, generators, files. You can also unpack in a for loop: for x, y in [(1,2),(3,4)]:. Nested unpacking (a, (b, c)) = (1, (2, 3)) works but hurts readability; prefer flatter structures.

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