Python typing
From wikinotes
Type annotations in python.
Example
from typing import Dict, List, Tuple from typing import Optional, Union class Project: def ex_param_w_return(user: User) -> bool def ex_type_w_default(active: bool=False) -> None: def ex_no_return() -> None: def ex_generics(data: List[Dict]): def ex_optional() -> Optional[str]: # nullable type def ex_type_or_other_type(id: Union[str, int]) -> None:
Common Types
functions/lambdas
from typing import Callable def run_callback(cb: Callable[[str, int], bool]) -> None:dates/times
import datetime def foo() -> datetime.datetime: return datetime.datetime.now() def foo() -> datetime.date: return datetime.date.today()open file objects
from typing import IO # either bytes/str def foo() -> IO: return open('foo.txt', 'r') def foo() -> IO[bytes]: return open('foo.txt', 'rb') def foo() -> IO[str]: return open('foo.txt', 'r')context managers
@contextlib.contextmanager def foo() -> Iterator[str]: print('foo') yield 'bar' print('baz')dataclasses (structs)
They're already typed. See python datatypes
import dataclasses @dataclasses.dataclass class User id: int name: str
Implementing Generics
TODO:
improve, w/ usage example
from typing import Generic, TypeVar T = TypeVar('T') class Range(Generic[T]): start: T end: T