enumerate, zip, and sorted(key=...)

Three builtins replace a lot of manual index juggling.

enumerate

When you need both the index and the value, do not reach for range(len(...)). Use enumerate:

names = ["Ada", "Linus", "Grace"]
for i, name in enumerate(names):
    print(i, name)
# 0 Ada / 1 Linus / 2 Grace

# start counting from 1
for rank, name in enumerate(names, start=1):
    print(rank, name)

zip

zip walks two (or more) sequences in lockstep, pairing items by position:

names = ["Ada", "Linus"]
ages = [36, 54]
for name, age in zip(names, ages):
    print(f"{name} is {age}")

pairs = dict(zip(names, ages))  # {'Ada': 36, 'Linus': 54}

sorted with a key

sorted returns a new sorted list. The key argument takes a function that maps each item to the value you want to sort by. A lambda is a tiny inline function, perfect for this:

people = [("Ada", 36), ("Grace", 85), ("Linus", 54)]
by_age = sorted(people, key=lambda p: p[1])
oldest_first = sorted(people, key=lambda p: p[1], reverse=True)

The key runs once per item; Python sorts by the values it returns.