typing-derive

derive types from other types to make it easier to type code!

Installation

pip install typing-derive

usage

add as a mypy plugin

[mypy]
plugins = typing_derive.plugin

typing_derive.impl.typeddict_from_func

create a usable TypedDict from some callable. useful if you need to dynamically build up **kwargs to call a function

from typing_derive.impl import typeddict_from_func

def f(x: int, y: str) -> None: ...

TD = typeddict_from_func('TD', f)

x: TD = {
    'x': 1,
    'y': 'hello hello',
}

f(**x)

typing_derive.impl.typeof

create a type alias for the type of a function / variable.

one use might be to pass functions of matching signatures as objects

def f(x: int, y: str) -> None: ...

F = typeof('F', f)

def g(func: F) -> None:
    func(x=1, y='two')

def h(x: int, y: str) -> None: ...
def j(x: str, y: str) -> None: ...
def k(x1: int, y: str) -> None: ...

g(f)  # ok
g(h)  # ok
g(j)  # error: `x` is `str` not `int`
g(k)  # error: `x1` mismatches `x`

it also just works on normal variables too -- though I haven't come up with a use for this yet

x = 5

X = typeof('X', x)  # effectively `type X = int`

y: X = 6  # ok
z: X = 'no'  # not ok!