What are some examples of using the typing module and typing extensions in Python?

What are some examples of using the typing module and typing extensions in Python?

The typing module in Python provides support for type hints. For example, you can use List and Dict to specify types for collections. Here's a simple example:

from typing import List, Dict

def process_items(items: List[str]) -> Dict[str, int]:
    return {item: len(item) for item in items}

This function takes a list of strings and returns a dictionary with the string as the key and its length as the value.

Can you explain what typing extensions are?

Typing extensions are additional features that are not yet part of the standard typing module but are useful for type hinting. For example, Literal and Final are part of typing extensions. Here's how you can use Literal:

from typing_extensions import Literal

def handle_status(status: Literal['success', 'error']) -> None:
    print(f'Status: {status}')

This function restricts the status parameter to only accept 'success' or 'error'.

What are some common use cases for type hints?

Common use cases for type hints include improving code readability, enabling better IDE support, and catching type-related errors during development. They are especially useful in large codebases where understanding the expected types can help maintain the code.

Are there any performance implications of using type hints?

No, type hints are not enforced at runtime and do not affect performance. They are mainly for static type checkers and IDEs to help developers catch errors early.