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"""Non-pipable creation operators."""
from __future__ import annotations
import sys
import asyncio
import inspect
import builtins
import itertools
from typing import (
AsyncIterable,
Awaitable,
Iterable,
Protocol,
TypeVar,
AsyncIterator,
cast,
)
from typing_extensions import ParamSpec
from ..stream import time
from ..core import operator, streamcontext
__all__ = [
"iterate",
"preserve",
"just",
"call",
"throw",
"empty",
"never",
"repeat",
"range",
"count",
]
T = TypeVar("T")
P = ParamSpec("P")
# Hack for python 3.8 compatibility
if sys.version_info < (3, 9):
P = TypeVar("P")
# Convert regular iterables
@operator
async def from_iterable(it: Iterable[T]) -> AsyncIterator[T]:
"""Generate values from a regular iterable."""
for item in it:
await asyncio.sleep(0)
yield item
@operator
def from_async_iterable(ait: AsyncIterable[T]) -> AsyncIterator[T]:
"""Generate values from an asynchronous iterable.
Note: the corresponding iterator will be explicitely closed
when leaving the context manager."""
return streamcontext(ait)
@operator
def iterate(it: AsyncIterable[T] | Iterable[T]) -> AsyncIterator[T]:
"""Generate values from a sychronous or asynchronous iterable."""
if isinstance(it, AsyncIterable):
return from_async_iterable.raw(it)
if isinstance(it, Iterable):
return from_iterable.raw(it)
raise TypeError(f"{type(it).__name__!r} object is not (async) iterable")
@operator
async def preserve(ait: AsyncIterable[T]) -> AsyncIterator[T]:
"""Generate values from an asynchronous iterable without
explicitly closing the corresponding iterator."""
async for item in ait:
yield item
# Simple operators
@operator
async def just(value: T) -> AsyncIterator[T]:
"""Await if possible, and generate a single value."""
if inspect.isawaitable(value):
yield await value
else:
yield value
Y = TypeVar("Y", covariant=True)
class SyncCallable(Protocol[P, Y]):
def __call__(self, *args: P.args, **kwargs: P.kwargs) -> Y:
...
class AsyncCallable(Protocol[P, Y]):
def __call__(self, *args: P.args, **kwargs: P.kwargs) -> Awaitable[Y]:
...
@operator
async def call(
func: SyncCallable[P, T] | AsyncCallable[P, T], *args: P.args, **kwargs: P.kwargs
) -> AsyncIterator[T]:
"""Call the given function and generate a single value.
Await if the provided function is asynchronous.
"""
if asyncio.iscoroutinefunction(func):
async_func = cast("AsyncCallable[P, T]", func)
yield await async_func(*args, **kwargs)
else:
sync_func = cast("SyncCallable[P, T]", func)
yield sync_func(*args, **kwargs)
@operator
async def throw(exc: Exception) -> AsyncIterator[None]:
"""Throw an exception without generating any value."""
if False:
yield
raise exc
@operator
async def empty() -> AsyncIterator[None]:
"""Terminate without generating any value."""
if False:
yield
@operator
async def never() -> AsyncIterator[None]:
"""Hang forever without generating any value."""
if False:
yield
future: asyncio.Future[None] = asyncio.Future()
try:
await future
finally:
future.cancel()
@operator
def repeat(
value: T, times: int | None = None, *, interval: float = 0.0
) -> AsyncIterator[T]:
"""Generate the same value a given number of times.
If ``times`` is ``None``, the value is repeated indefinitely.
An optional interval can be given to space the values out.
"""
args = () if times is None else (times,)
it = itertools.repeat(value, *args)
agen = from_iterable.raw(it)
return time.spaceout.raw(agen, interval) if interval else agen
# Counting operators
@operator
def range(*args: int, interval: float = 0.0) -> AsyncIterator[int]:
"""Generate a given range of numbers.
It supports the same arguments as the builtin function.
An optional interval can be given to space the values out.
"""
agen = from_iterable.raw(builtins.range(*args))
return time.spaceout.raw(agen, interval) if interval else agen
@operator
def count(
start: int = 0, step: int = 1, *, interval: float = 0.0
) -> AsyncIterator[int]:
"""Generate consecutive numbers indefinitely.
Optional starting point and increment can be defined,
respectively defaulting to ``0`` and ``1``.
An optional interval can be given to space the values out.
"""
agen = from_iterable.raw(itertools.count(start, step))
return time.spaceout.raw(agen, interval) if interval else agen
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