Type Hints

def greet(name: str) -> str:
    return "Hello, " + name

print(greet("World"))

age: int = 25
height: float = 1.75
name: str = "Ada"
print(age, height, name)

from typing import List
def total(nums: List[int]) -> int:
    return sum(nums)

print(total([1, 2, 3, 4]))

from typing import Optional
def find(x: int) -> Optional[str]:
    if x > 0:
        return "positive"
    return None

print(find(5))
print(find(-1))

def min_max(numbers: list[int]) -> tuple[int, int]:
    return min(numbers), max(numbers)

low, high = min_max([4, 9, 1, 7])
print(low, high)

# *tags: str means every extra positional argument is a str.
# **scores: int means every keyword argument's value is an int.
def describe(*tags: str, **scores: int) -> str:
    total = sum(scores.values())
    return f"{', '.join(tags)}: {total} points"

print(describe("math", "quiz", alice=8, bob=7))

from collections.abc import Iterator

def countdown(n: int) -> Iterator[int]:
    while n > 0:
        yield n
        n -= 1

print(list(countdown(3)))