7. Function Annotations

These examples demonstrate how function annotations can be used to improve code readability, documentation, and static analysis. Although Python itself doesn’t enforce type annotations at runtime, tools like mypy can use these annotations for type checking.

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1. Basic Function Annotations

def greet(name: str) -> str:
    return f"Hello, {name}!"

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

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2. Annotating Multiple Arguments

def add(x: int, y: int) -> int:
    return x + y

print(add(10, 20))  # Output: 30

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3. Using Annotations with Default Values

def power(base: int, exponent: int = 2) -> int:
    return base ** exponent

print(power(5))       # Output: 25
print(power(5, 3))    # Output: 125

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4. Annotations for Custom Types

from typing import List

def total(scores: List[int]) -> int:
    return sum(scores)

print(total([90, 85, 88]))  # Output: 263

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5. Annotations for Optional Parameters

from typing import Optional

def find_user(username: str, age: Optional[int] = None) -> str:
    return f"User: {username}, Age: {age if age else 'Unknown'}"

print(find_user("Alice"))           # Output: User: Alice, Age: Unknown
print(find_user("Bob", age=25))     # Output: User: Bob, Age: 25

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6. Annotations for Callable Objects

from typing import Callable

def execute(func: Callable[[int, int], int], a: int, b: int) -> int:
    return func(a, b)

print(execute(lambda x, y: x + y, 10, 20))  # Output: 30

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7. Annotations with Dictionaries

from typing import Dict

def user_info(data: Dict[str, str]) -> str:
    return f"Name: {data['name']}, Age: {data['age']}"

print(user_info({"name": "Alice", "age": "25"}))  # Output: Name: Alice, Age: 25

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8. Annotations with Tuples

from typing import Tuple

def get_coordinates() -> Tuple[float, float]:
    return 40.7128, -74.0060

print(get_coordinates())  # Output: (40.7128, -74.0060)

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9. Annotations for Generator Functions

from typing import Generator

def count_up_to(max_val: int) -> Generator[int, None, None]:
    count = 1
    while count <= max_val:
        yield count
        count += 1

for num in count_up_to(5):
    print(num, end=" ")  # Output: 1 2 3 4 5

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10. Accessing Function Annotations

def multiply(a: int, b: int) -> int:
    return a * b

print(multiply.__annotations__)
# Output: {'a': <class 'int'>, 'b': <class 'int'>, 'return': <class 'int'>}

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