jorenham

original post: scipy/scipy-stubs#153 (comment)

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Annotating a function whose return type depends on an optional positional- or keyword-only parameter in Python

Overloads are roughly similar to pattern matching[^1], but from the perspective of the caller.

Consider this function for example

jorenham

Without scipy-stubs	With scipy-stubs

• VSCode 1.96.2
• PyLance 2024.12.100
• pyright == 1.1.391
• scipy == 1.15.0

jorenham

import itertools, typing

def primes(n: int, /) -> typing.Generator[int, None, None]:
    yield(next(sieve := itertools.count(prime := 2)))
    for _ in range(n):
        yield (prime := next(sieve := filter(prime.__rmod__, sieve)))

jorenham

from __future__ import annotations
from typing import Protocol


class _Int(Protocol):
    def __int__(self) -> int: ...
    def __pos__(self) -> _Int: ...
    def __neg__(self) -> _Int: ...

jorenham

import asyncio
import time
from time import perf_counter_ns


# noinspection PyPep8Naming
class ns_per_it:
    __slots__ = 'n', 'res'

    def __init__(self, n: int):

jorenham

import asyncio


class AsyncInit:
    def __await__(self):
        async def _():
            await self.__ainit__()
            return self
        return _().__await__()

jorenham

import contextlib
from typing import ContextManager

from django.core import cache
from django.core.cache.backends.dummy import DummyCache


@contextlib.contextmanager
def disable_caches(*aliases: str) -> ContextManager[tuple[str, ...]]:
    """Temporarily disable django caching backends. By default, all connected

jorenham

from typing import Optional, TYPE_CHECKING

if TYPE_CHECKING:
    from _typeshed import SupportsLessThan


def cmp(a: 'SupportsLessThan', b: 'SupportsLessThan') -> Optional[int]:
    """Return 1 if a > b, 0 if a == b, -1 if a < b, otherwise None.

    >>> cmp(42, 69), cmp(666, 666), cmp(69, 42), cmp(0, float('nan'))

jorenham

class FancyGeneric:
    def __class_getitem__(cls, params):
        if not isinstance(params, tuple):
            params = (params,)

        newparams = []
        for param in params:
            if isinstance(param, slice):
                assert param.start is None and param.step is None

jorenham

import sys

for x in (0.0, 1/10, -1/10, sys.float_info.max, sys.float_info.min, float('inf'), float('-inf'), float('NaN')):
    print(f'{x}++ => {float_incr(x)}')

i, xi = 0, float('-inf')
while xi < float('inf'):
    x = float_incr(xi)
    assert x > xi
    xi = x / 2 if x < 0 else x * 2