97. Function Annotations for Type Hints

Here are 10 Python code snippets demonstrating function annotations for type hints to improve code clarity and documentation:

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1. Basic Type Hints for Arguments and Return Types

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def add_numbers(a: int, b: int) -> int:
    return a + b

result = add_numbers(5, 10)
print(result)  # Output: 15

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2. Type Hinting with Optional Arguments

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from typing import Optional

def greet(name: Optional[str] = None) -> str:
    return f"Hello, {name if name else 'Guest'}!"

print(greet())           # Output: Hello, Guest!
print(greet("Alice"))    # Output: Hello, Alice!

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3. Type Hints for Lists

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from typing import List

def calculate_average(numbers: List[float]) -> float:
    return sum(numbers) / len(numbers)

print(calculate_average([1.5, 2.5, 3.0]))  # Output: 2.3333333333333335

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4. Type Hints for Dictionaries

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from typing import Dict

def get_price(product: str, price_list: Dict[str, float]) -> float:
    return price_list.get(product, 0.0)

prices = {"apple": 1.5, "banana": 0.5}
print(get_price("apple", prices))  # Output: 1.5
print(get_price("orange", prices)) # Output: 0.0

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5. Type Hints for Tuples

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from typing import Tuple

def get_coordinates() -> Tuple[float, float]:
    return (37.7749, -122.4194)

print(get_coordinates())  # Output: (37.7749, -122.4194)

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6. Type Hints for Callable (Functions as Arguments)

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from typing import Callable

def execute(func: Callable[[int, int], int], x: int, y: int) -> int:
    return func(x, y)

result = execute(lambda a, b: a * b, 4, 5)
print(result)  # Output: 20

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7. Type Hints for Iterables

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from typing import Iterable

def total_length(strings: Iterable[str]) -> int:
    return sum(len(s) for s in strings)

print(total_length(["hello", "world"]))  # Output: 10

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8. Custom Types

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from typing import List, TypeAlias

Vector: TypeAlias = List[float]

def scale_vector(v: Vector, scalar: float) -> Vector:
    return [x * scalar for x in v]

print(scale_vector([1.0, 2.0, 3.0], 2.0))  # Output: [2.0, 4.0, 6.0]

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9. Union for Multiple Accepted Types

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from typing import Union

def parse_input(value: Union[str, int]) -> int:
    if isinstance(value, str):
        return int(value)
    return value

print(parse_input("42"))  # Output: 42
print(parse_input(42))    # Output: 42

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10. Type Hints for Generators

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from typing import Generator

def countdown(start: int) -> Generator[int, None, None]:
    while start > 0:
        yield start
        start -= 1

for num in countdown(5):
    print(num)  # Output: 5, 4, 3, 2, 1

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