Python · Tuples and unpacking

A tuple is an immutable sequence. I use one when a group of values belongs together and shouldn’t change, such as a coordinate or a database row. Because tuples are immutable (and hashable when their items are), they can be dictionary keys.

It’s the comma that makes a tuple. (5) is just the int 5, while (5,) and 5, are one-element tuples.

Unpacking assigns the items of a sequence to several names at once:

• x, y = point
• a, b = b, a swaps two values with no temporary variable
• first, *rest = items collects whatever is left into a list (PEP 3132)

collections.namedtuple lets you access the fields by name, which makes the code easier to read.

from collections import namedtuple

point = (3, 4)
x, y = point
print(x, y, type((5)).__name__, type((5,)).__name__)

a, b = 1, 2
a, b = b, a
print(a, b)

first, *middle, last = [10, 20, 30, 40, 50]
print(first, middle, last)

Student = namedtuple("Student", ["name", "branch", "year"])
s = Student("Sahaj", "ICT", 2023)
print(s.name, s.branch, s[2])
print({(0, 0): "origin"}[(0, 0)])

Output:

3 4 int tuple
2 1
10 [20, 30, 40] 50
Sahaj ICT 2023
origin