How to Specify Multiple Return Types in Python Using Type Hints?

Specifying Multiple Return Types in Python Using Type Hints

In Python, functions can return values of various types. When multiple return types are possible, type hints can enhance the readability and maintainability of code.

How to Specify Multiple Return Types

From Python 3.10 onwards, the vertical bar (|) syntax can be used to specify unions. For example, the following function can return either a list or a bool:

def foo(id) -> list | bool:
    ...

For Python versions prior to 3.10, the typing.Union type hint can be used:

from typing import Union

def foo(id) -> Union[list, bool]:
    ...

Example Usage

The following function retrieves an element from a list or returns False if the element is not found:

def get_element(elements, index):
    try:
        return elements[index]
    except IndexError:
        return False

Using type hints, we can specify the return types as:

def get_element(elements, index) -> list | bool:
    try:
        return elements[index]
    except IndexError:
        return False

Limitations

Type hints are not enforced at runtime. Python remains a dynamically-typed language, and type checking occurs during development. This allows flexibility but may introduce runtime errors.

Additional Information

For more information, refer to:

• [PEP 483 - Type Hints](https://www.python.org/dev/peps/pep-0483/)
• [PEP 484 - Type Hints in Python 3.5 ](https://www.python.org/dev/peps/pep-0484/)

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