JuniorTheoryCommon

What does the program print?

Python

people = [("ann", 31), ("bob", 25), ("cid", 31)]
by_age = sorted(people, key=lambda p: p[1])
print([name for name, age in by_age])

['bob', 'ann', 'cid']

Expecting cid before ann: sorted is stable, so items with equal keys keep their original order, and ann came before cid in people.
Expecting the names in their original order: key=lambda p: p[1] makes sorted compare only the ages, so bob, aged 25, comes first.

JuniorTheoryCommon

Python

people = [("ann", 31), ("bob", 25), ("cid", 31)]
by_age = sorted(people, key=lambda p: p[1])
print([name for name, age in by_age])

['bob', 'ann', 'cid']

Expecting cid before ann: sorted is stable, so items with equal keys keep their original order, and ann came before cid in people.
Expecting the names in their original order: key=lambda p: p[1] makes sorted compare only the ages, so bob, aged 25, comes first.