Python Typing

Simple typing syntax for Python variables, functions and classes with the typing library.

from typing import ...

• https://docs.python.org/3/library/typing.html

Note

For more specific data validation, use Pydantic models.

• https://docs.pydantic.dev/

pip install pydantic

Function Inputs

Easy Usage

def add(a: int, b: int) -> int:
    return a + b

• a, b are int type
• func returns int type

Lists / Dicts

def process(items: list[int]):
    pass

• items is a list of int type

def process(items: dict[str, int]):
    pass

• items is a dict with str keys and int values

Optional

from typing import Optional

def process(a: int, b: Optional[int] = 0):
    pass

• b is optional and defaults to 0

Union

from typing import Union

def process(a: Union[int, str]):
    pass

• a can be int or str type

Function Outputs

Return Values

def process() -> list[int]:
    return [1, 2, 3]

• process returns a list of int type

def process() -> tuple[str, int]:
    return 'a', 1

• process returns a tuple of str and int type

Return None

def process() -> None:
    pass

• process returns None

Classes

Class Attributes

class A:
    def __init__(self, a: int):
        self.a = a

def process(a: A):
    pass

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