mypy-play

from typing import Iterator


def fib(n: int) -> Iterator[int]:
    a, b = 0, 1
    while a < n:
        yield a
        a, b = b, a + b

mypy-play

from typing import Literal, Optional, overload

@overload
def gimme(x: Literal[True]) -> str: ...
@overload
def gimme(x: Literal[False]) -> None: ...
@overload
def gimme(x: bool) -> Optional[str]: ...

def gimme(x: bool) -> Optional[str]:

mypy-play

from typing import Any


def foo(x: Any) -> None:
    pass


class Bar():

    pass

mypy-play

import typing as tp
if not tp.TYPE_CHECKING:
    reveal_type = lambda var: var


class Foo:  # Only supports "*Foo*".
    def __init__(self, value: int) -> None:
        self.value = value
    
    def __add__(self, other: tp.Union["Foo", "FooBar"]) -> "Foo":

mypy-play

from fractions import Fraction
import decimal as dec
import typing as tp
if not tp.TYPE_CHECKING:
    reveal_type = lambda var: var

Real = tp.Union[int, float, Fraction]
Decimal = tp.Union[dec.Decimal, int]
T1 = tp.TypeVar("T1", Real, Decimal)

mypy-play

from typing import Any
from dataclasses import is_dataclass


def example1(arg: Any) -> None:
    if is_dataclass(arg):
        reveal_type(arg)  # ❌ Revealed type is "type[_typeshed.DataclassInstance]"


def example2(arg: object) -> None:

mypy-play

class Base:...
class Foo(Base):...
a: Base
b: int|None = {Foo:1}.get(type(a))

mypy-play

a: object = 1
reveal_type(a)

mypy-play

from typing import TypeVar

T1 = TypeVar("T1")
T2 = TypeVar("T2")


def f(t1: T1, t2: T2) -> T1 | T2:
    return t1

mypy-play

from typing import TypeVar

T1 = TypeVar("T2")
T2 = TypeVar("T2")


def f(t1: T1, t2: T2) -> T1 | T2: ...


b: int = f(1, None) or 1