Tuples and Unpacking

Why this matters

Sometimes two or three values belong together: a name and a score, an x and a y. A tuple groups them. It looks like a list but uses round brackets, and it cannot be changed after it is made. That makes it a safe way to say “these values travel together”.

The idea

point = (3, 4)
print(point[0])      # 3
x, y = point         # unpacking: x is 3, y is 4

Unpacking copies the items of a tuple (or list) into separate variables in one line. It also gives Python’s neat swap:

a, b = 1, 2
a, b = b, a          # now a is 2 and b is 1

zip walks through several lists in step, handing you a tuple at each position:

names = ["Ada", "Bo"]
ages = [36, 41]
for name, age in zip(names, ages):
    print(name, age)

Tuples compare item by item from the left, so (90, "Bo") > (85, "Ada") is True. That makes max() on a list of (score, name) pairs pick the highest score.

Try it

Unpack (1, 2, 3) into a, b, c. Then try point[0] = 9 on the tuple above and read the TypeError.

Your turn

The starter reads two lines: names (words) and scores (whole numbers), in the same order. Do two things:

1. Print one line per person, like Ada: 90.
2. Then print who scored highest, like Best: Ada (90).

For the input Ada Bo Cy and 90 85 70 the output is:

Ada: 90
Bo: 85
Cy: 70
Best: Ada (90)

(The checks never contain a tie for the top score.)

Recap

• A tuple (a, b) is a fixed group of values; lists use [] and can change, tuples cannot.
• Unpacking x, y = point splits a group into variables; zip pairs up lists.
• Tuples compare left to right, so max of (score, name) pairs finds the top score.

Common mistakes

• Trying to change a tuple: TypeError: 'tuple' object does not support item assignment. Build a new one instead.
• Unpacking the wrong number of items: ValueError: too many values to unpack.
• Forgetting the comma in a one-item tuple: (5,) is a tuple, (5) is just the number 5.