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

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

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

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

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

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)

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

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

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

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

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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These examples illustrate how type hints improve code readability and provide valuable documentation, helping developers understand the expected types of arguments and return values. Although type hints don’t enforce types at runtime, they enhance static analysis and integrate seamlessly with tools like mypy for type checking.