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from __future__ import annotations
import sys
from abc import ABCMeta, abstractmethod
from collections.abc import Awaitable, Callable
from types import TracebackType
from typing import TYPE_CHECKING, Any, Protocol, TypeVar, overload
if sys.version_info >= (3, 11):
from typing import TypeVarTuple, Unpack
else:
from typing_extensions import TypeVarTuple, Unpack
if TYPE_CHECKING:
from .._core._tasks import CancelScope
T_Retval = TypeVar("T_Retval")
T_contra = TypeVar("T_contra", contravariant=True)
PosArgsT = TypeVarTuple("PosArgsT")
class TaskStatus(Protocol[T_contra]):
@overload
def started(self: TaskStatus[None]) -> None:
...
@overload
def started(self, value: T_contra) -> None:
...
def started(self, value: T_contra | None = None) -> None:
"""
Signal that the task has started.
:param value: object passed back to the starter of the task
"""
class TaskGroup(metaclass=ABCMeta):
"""
Groups several asynchronous tasks together.
:ivar cancel_scope: the cancel scope inherited by all child tasks
:vartype cancel_scope: CancelScope
"""
cancel_scope: CancelScope
@abstractmethod
def start_soon(
self,
func: Callable[[Unpack[PosArgsT]], Awaitable[Any]],
*args: Unpack[PosArgsT],
name: object = None,
) -> None:
"""
Start a new task in this task group.
:param func: a coroutine function
:param args: positional arguments to call the function with
:param name: name of the task, for the purposes of introspection and debugging
.. versionadded:: 3.0
"""
@abstractmethod
async def start(
self,
func: Callable[..., Awaitable[Any]],
*args: object,
name: object = None,
) -> Any:
"""
Start a new task and wait until it signals for readiness.
:param func: a coroutine function
:param args: positional arguments to call the function with
:param name: name of the task, for the purposes of introspection and debugging
:return: the value passed to ``task_status.started()``
:raises RuntimeError: if the task finishes without calling
``task_status.started()``
.. versionadded:: 3.0
"""
@abstractmethod
async def __aenter__(self) -> TaskGroup:
"""Enter the task group context and allow starting new tasks."""
@abstractmethod
async def __aexit__(
self,
exc_type: type[BaseException] | None,
exc_val: BaseException | None,
exc_tb: TracebackType | None,
) -> bool | None:
"""Exit the task group context waiting for all tasks to finish."""
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