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import math
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import sys
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import threading
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from contextlib import contextmanager
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from importlib import import_module
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from typing import (
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Any,
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Callable,
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Coroutine,
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Dict,
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Generator,
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Optional,
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Tuple,
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Type,
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TypeVar,
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)
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import sniffio
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# This must be updated when new backends are introduced
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from ._compat import DeprecatedAwaitableFloat
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BACKENDS = "asyncio", "trio"
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T_Retval = TypeVar("T_Retval")
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threadlocals = threading.local()
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def run(
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func: Callable[..., Coroutine[Any, Any, T_Retval]],
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*args: object,
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backend: str = "asyncio",
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backend_options: Optional[Dict[str, Any]] = None,
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) -> T_Retval:
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"""
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Run the given coroutine function in an asynchronous event loop.
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The current thread must not be already running an event loop.
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:param func: a coroutine function
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:param args: positional arguments to ``func``
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:param backend: name of the asynchronous event loop implementation – currently either
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``asyncio`` or ``trio``
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:param backend_options: keyword arguments to call the backend ``run()`` implementation with
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(documented :ref:`here <backend options>`)
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:return: the return value of the coroutine function
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:raises RuntimeError: if an asynchronous event loop is already running in this thread
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:raises LookupError: if the named backend is not found
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"""
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try:
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asynclib_name = sniffio.current_async_library()
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except sniffio.AsyncLibraryNotFoundError:
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pass
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else:
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raise RuntimeError(f"Already running {asynclib_name} in this thread")
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try:
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asynclib = import_module(f"..._backends._{backend}", package=__name__)
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except ImportError as exc:
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raise LookupError(f"No such backend: {backend}") from exc
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token = None
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if sniffio.current_async_library_cvar.get(None) is None:
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# Since we're in control of the event loop, we can cache the name of the async library
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token = sniffio.current_async_library_cvar.set(backend)
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try:
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backend_options = backend_options or {}
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return asynclib.run(func, *args, **backend_options)
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finally:
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if token:
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sniffio.current_async_library_cvar.reset(token)
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async def sleep(delay: float) -> None:
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"""
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Pause the current task for the specified duration.
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:param delay: the duration, in seconds
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"""
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return await get_asynclib().sleep(delay)
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async def sleep_forever() -> None:
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"""
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Pause the current task until it's cancelled.
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This is a shortcut for ``sleep(math.inf)``.
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.. versionadded:: 3.1
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"""
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await sleep(math.inf)
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async def sleep_until(deadline: float) -> None:
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"""
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Pause the current task until the given time.
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:param deadline: the absolute time to wake up at (according to the internal monotonic clock of
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the event loop)
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.. versionadded:: 3.1
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"""
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now = current_time()
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await sleep(max(deadline - now, 0))
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def current_time() -> DeprecatedAwaitableFloat:
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"""
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Return the current value of the event loop's internal clock.
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:return: the clock value (seconds)
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"""
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return DeprecatedAwaitableFloat(get_asynclib().current_time(), current_time)
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def get_all_backends() -> Tuple[str, ...]:
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"""Return a tuple of the names of all built-in backends."""
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return BACKENDS
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def get_cancelled_exc_class() -> Type[BaseException]:
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"""Return the current async library's cancellation exception class."""
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return get_asynclib().CancelledError
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#
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# Private API
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#
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@contextmanager
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def claim_worker_thread(backend: str) -> Generator[Any, None, None]:
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module = sys.modules["anyio._backends._" + backend]
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threadlocals.current_async_module = module
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try:
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yield
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finally:
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del threadlocals.current_async_module
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def get_asynclib(asynclib_name: Optional[str] = None) -> Any:
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if asynclib_name is None:
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asynclib_name = sniffio.current_async_library()
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modulename = "anyio._backends._" + asynclib_name
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try:
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return sys.modules[modulename]
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except KeyError:
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return import_module(modulename)
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