Functions

Specify return type

In Python, you can specify the return type of a function using type hints. Type hints are a way to document the expected types of function arguments and return values. However, Python’s runtime does not enforce these type annotations. They are intended to be used by tools like type checkers, IDEs, and linters.

To specify the return type of a function, you can follow the function definition with an arrow (->) and the type. For example:

def greeting(name: str) -> str:
    return 'Hello ' + name

In this example, the function greeting takes one argument name of type str and returns a value of type str.

If your function can return multiple types, you can use the Union type from the typing module to specify multiple possible return types. Here’s an example:

from typing import Union

def parse_email(email: str) -> Union[str, tuple]:
    # ... parse the email ...
    if email_is_valid:
        return 'valid'
    else:
        return 'invalid', 42

In this example, the function parse_email can return either a string (if the email is valid) or a tuple (if the email is invalid).

For more complex scenarios, where you want to specify the type of the elements in a tuple, you can use a tuple type. Here’s an example:

from typing import Tuple

def parse_node_info() -> Tuple[str, str, int]:
    # ... parse node info ...
    return node_id, node_name, uptime_minutes

In this example, the function parse_node_info returns a tuple with three elements: a string, a string, and an integer.

Note that type hints are optional in Python and are intended to help with readability and maintainability, rather than enforcing strict type checking at runtime.

Examples

def func(data: str) -> str:
    return data

def func(numbers: list[int]) -> list[int]:
    numbers.reverse()
    return numbers

# *args, *numbers, *foobar
def sum_numbers(*args: float) -> float:
    return sum(args)
    
print(sum_numbers(1, 2, 3, 4, 5, 10, 20))