hat-aio 0.4.1.dev20210212

Hat async utility library

This library is part of Hat Open project - open-source framework of tools and libraries for developing applications used for remote monitoring, control and management of intelligent electronic devices such as IoT devices, PLCs, industrial automation or home automation systems.

Development of Hat Open and associated repositories is sponsored by Končar - Power Plant and Electric Traction Engineering Inc. (Končar KET - https://www.koncar-ket.hr).

For more information see:

• hat-aio documentation - https://core.hat-open.com/docs/libraries/aio.html

• Hat Core homepage - https://core.hat-open.com

• Hat Core git repository - https://github.com/hat-open/hat-core.git

Warning

This project is currently in state of active development. Features, functionality and API are unstable.

About

Async utility functions.

• hat.aio.first:

  async def first(xs: typing.AsyncIterable[T],
                  fn: typing.Callable[[T], bool] = lambda _: True,
                  default: typing.Optional[T] = None
                  ) -> typing.Optional[T]:
      """Return the first element from async iterable that satisfies
      predicate `fn`, or `default` if no such element exists.
  
      Args:
          xs: async collection
          fn: predicate
          default: default value
  
      Example::
  
          async def async_range(x):
              for i in range(x):
                  await asyncio.sleep(0)
                  yield i
  
          assert await first(async_range(3)) == 0
          assert await first(async_range(3), lambda x: x > 1) == 2
          assert await first(async_range(3), lambda x: x > 2) is None
          assert await first(async_range(3), lambda x: x > 2, 123) == 123
  
      """

• hat.aio.uncancellable:

  async def uncancellable(f: asyncio.Future,
                          raise_cancel: bool = True
                          ) -> typing.Any:
      """Uncancellable execution of a Future.
  
      Future is shielded and its execution cannot be interrupted.
  
      If `raise_cancel` is `True` and the Future gets canceled,
      `asyncio.CancelledError` is reraised after the Future finishes.
  
      Warning:
          If `raise_cancel` is `False`, this method suppresses
          `asyncio.CancelledError` and stops its propagation. Use with
          caution.
  
      Args:
          f: future
          raise_cancel: raise CancelledError flag
  
      Returns:
          future's result
  
      """

• hat.aio.call, hat.aio.call_on_cancel and hat.aio.call_on_done:

  async def call(fn: AsyncCallable, *args, **kwargs) -> typing.Any:
      """Call a function or a coroutine (or other callable object).
  
      Call the `fn` with `args` and `kwargs`. If result of this call is
      awaitable, it is awaited and returned. Otherwise, result is immediately
      returned.
  
      Args:
          fn: callable object
          args: additional positional arguments
          kwargs: additional keyword arguments
  
      Returns:
          awaited result or result
  
      Example:
  
          def f1(x):
              return x
  
          def f2(x):
              f = asyncio.Future()
              f.set_result(x)
              return f
  
          async def f3(x):
              return x
  
          assert 'f1' == await hat.aio.call(f1, 'f1')
          assert 'f2' == await hat.aio.call(f2, 'f2')
          assert 'f3' == await hat.aio.call(f3, 'f3')
  
      """
  
  async def call_on_cancel(fn: AsyncCallable, *args, **kwargs) -> typing.Any:
      """Call a function or a coroutine when canceled.
  
      When canceled, `fn` is called with `args` and `kwargs` by using
      `call` coroutine.
  
      Args:
          fn: function or coroutine
          args: additional function arguments
          kwargs: additional function keyword arguments
  
      Returns:
          function result
  
      Example::
  
          f = asyncio.Future()
          group = Group()
          group.spawn(call_on_cancel, f.set_result, 123)
          assert not f.done()
          await group.async_close()
          assert f.result() == 123
  
      """
  
  async def call_on_done(f: typing.Awaitable,
                         fn: AsyncCallable,
                         *args, **kwargs
                         ) -> typing.Any:
      """Call a function or a coroutine when awaitable is done.
  
      When `f` is done, `fn` is called with `args` and `kwargs` by using
      `call` coroutine.
  
      If this coroutine is canceled before `f` is done, `f` is canceled and `fn`
      is not called.
  
      If this coroutine is canceled after `f` is done, `fn` call is canceled.
  
      Args:
          f: awaitable future
          fn: function or coroutine
          args: additional function arguments
          kwargs: additional function keyword arguments
  
      Returns:
          function result
  
      Example::
  
          f = asyncio.Future()
          group = Group()
          group.spawn(call_on_done, f, group.close)
          assert group.is_open
          f.set_result(None)
          await group.wait_closed()
          assert group.is_closed
  
      """

• hat.aio.create_executor:

  def create_executor(*args: typing.Any,
                      executor_cls: typing.Type = concurrent.futures.ThreadPoolExecutor,
                      loop: typing.Optional[asyncio.AbstractEventLoop] = None
                      ) -> typing.Callable[..., typing.Awaitable]:
      """Create `asyncio.loop.run_in_executor` wrapper.
  
      Returns a coroutine that takes a function and its arguments, executes the
      function using executor created from `executor_cls` and `args`; and
      returns the result.
  
      Args:
          args: executor args
          executor_cls: executor class
          loop: asyncio loop
  
      Returns:
          executor coroutine
  
      Example::
  
          executor1 = create_executor()
          executor2 = create_executor()
          tid1 = await executor1(threading.get_ident)
          tid2 = await executor2(threading.get_ident)
          assert tid1 != tid2
  
      """

• hat.aio.init_asyncio and hat.aio.run_asyncio:

  def init_asyncio(policy: typing.Optional[asyncio.AbstractEventLoopPolicy] = None):
      """Initialize asyncio.
  
      Sets event loop policy (if ``None``, instance of
      `asyncio.DefaultEventLoopPolicy` is used).
  
      After policy is set, new event loop is created and associated with current
      thread.
  
      On Windows, `asyncio.WindowsProactorEventLoopPolicy` is used as default
      policy.
  
      """
  
  def run_asyncio(future: typing.Awaitable, *,
                  handle_signals=True,
                  create_loop=False
                  ) -> typing.Any:
      """Run asyncio loop until the `future` is completed and return the result.
  
      If `handle_signals` is ``True``, SIGINT and SIGTERM handlers are
      temporarily overridden. Instead of raising ``KeyboardInterrupt`` on every
      signal reception, Future is canceled only once. Additional signals are
      ignored. On Windows, SIGBREAK (CTRL_BREAK_EVENT) handler is also
      overridden.
  
      If `create_loop` is set to ``True``, new event loop is created and set
      as thread's default event loop.
  
      On Windows, asyncio loop gets periodically woken up (every 0.5 seconds).
  
      Args:
          future: future or coroutine
          handle_signals: handle signals flag
          create_loop: create new event loop
  
      Returns:
          future's result
  
      Example::
  
          async def run():
              await asyncio.sleep(0)
              return 123
  
          result = run_asyncio(run())
          assert result == 123
  
      """

• hat.aio.Queue:

  class QueueClosedError(Exception):
      """Raised when trying to use a closed queue."""
  
  class QueueEmptyError(Exception):
      """Raised if queue is empty."""
  
  class QueueFullError(Exception):
      """Raised if queue is full."""
  
  class Queue:
      """Asyncio queue which implements AsyncIterable and can be closed.
  
      Interface and implementation are based on `asyncio.Queue`.
  
      If `maxsize` is less than or equal to zero, the queue size is infinite.
  
      Args:
          maxsize: maximum number of items in the queue
  
      Example::
  
          async def async_sum():
              result = 0
              async for i in queue:
                  result += i
              return result
  
          queue = Queue(maxsize=1)
          f = asyncio.ensure_future(async_sum())
          await queue.put(1)
          await queue.put(2)
          await queue.put(3)
          assert not f.done()
          queue.close()
          assert 6 == await f
  
      """
  
      def __init__(self, maxsize: int = 0): ...
  
      def __aiter__(self): ...
  
      async def __anext__(self): ...
  
      def __str__(self): ...
  
      def __len__(self): ...
  
      @property
      def maxsize(self) -> int:
          """Maximum number of items in the queue."""
  
      @property
      def is_closed(self) -> bool:
          """Is queue closed."""
  
      def empty(self) -> bool:
          """``True`` if queue is empty, ``False`` otherwise."""
  
      def full(self) -> bool:
          """``True`` if queue is full, ``False`` otherwise."""
  
      def qsize(self) -> int:
          """Number of items currently in the queue."""
  
      def close(self):
          """Close the queue."""
  
      def get_nowait(self) -> typing.Any:
          """Return an item if one is immediately available, else raise
          `QueueEmptyError`.
  
          Raises:
              QueueEmptyError
  
          """
  
      def put_nowait(self, item: typing.Any):
          """Put an item into the queue without blocking.
  
          If no free slot is immediately available, raise `QueueFullError`.
  
          Raises:
              QueueFullError
  
          """
  
      async def get(self) -> typing.Any:
          """Remove and return an item from the queue.
  
          If queue is empty, wait until an item is available.
  
          Raises:
              QueueClosedError
  
          """
  
      async def put(self, item: typing.Any):
          """Put an item into the queue.
  
          If the queue is full, wait until a free slot is available before adding
          the item.
  
          Raises:
              QueueClosedError
  
          """
  
      async def get_until_empty(self) -> typing.Any:
          """Empty the queue and return the last item.
  
          If queue is empty, wait until at least one item is available.
  
          Raises:
              QueueClosedError
  
          """
  
      def get_nowait_until_empty(self) -> typing.Any:
          """Empty the queue and return the last item if at least one
          item is immediately available, else raise `QueueEmptyError`.
  
          Raises:
              QueueEmptyError
  
          """

• hat.aio.Group:

  ExceptionCb = typing.Callable[[Exception], None]
  """Exception callback"""
  
  class Group:
      """Group of asyncio Tasks.
  
      Group enables creation and management of related asyncio Tasks. The
      Group ensures uninterrupted execution of Tasks and Task completion upon
      Group closing.
  
      Group can contain subgroups, which are independent Groups managed by the
      parent Group.
  
      If a Task raises exception, other Tasks continue to execute.
  
      If `exception_cb` handler is ``None``, exceptions are logged with level
      WARNING.
  
      """
  
      def __init__(self,
                   exception_cb: typing.Optional[ExceptionCb] = None,
                   *,
                   loop: typing.Optional[asyncio.AbstractEventLoop] = None): ...
  
      @property
      def is_open(self) -> bool:
          """``True`` if group is not closing or closed, ``False`` otherwise."""
  
      @property
      def is_closing(self) -> bool:
          """Is group closing or closed."""
  
      @property
      def is_closed(self) -> bool:
          """Is group closed."""
  
      async def wait_closing(self):
          """Wait until closing is ``True``."""
  
      async def wait_closed(self):
          """Wait until closed is ``True``."""
  
      def create_subgroup(self) -> 'Group':
          """Create new Group as a child of this Group. Return the new Group.
  
          When a parent Group gets closed, all of its children are closed.
          Closing of a subgroup has no effect on the parent Group.
  
          Subgroup inherits exception handler from its parent.
  
          """
  
      def wrap(self, future: asyncio.Future) -> asyncio.Task:
          """Wrap the Future into a Task and schedule its execution. Return the
          Task object.
  
          Resulting task is shielded and can be canceled only with
          `Group.async_close`.
  
          """
  
      def spawn(self, fn: typing.Callable[..., typing.Awaitable],
                *args, **kwargs) -> asyncio.Task:
          """Wrap the result of a `fn` into a Task and schedule its execution.
          Return the Task object.
  
          Function `fn` is called with provided `args` and `kwargs`.
          Resulting Task is shielded and can be canceled only with
          `Group.async_close`.
  
          """
  
      def close(self, cancel: bool = True):
          """Schedule Group closing.
  
          Closing Future is set immediately. All subgroups are closed, and all
          running tasks are optionally canceled. Once closing of all subgroups
          and execution of all tasks is completed, closed Future is set.
  
          Tasks are canceled if `cancel` is ``True``.
  
          """
  
      async def async_close(self, cancel: bool = True):
          """Close Group and wait until closed is ``True``."""
  
      async def __aenter__(self): ...
  
      async def __aexit__(self, *args): ...
  
  class Resource(abc.ABC):
      """Resource with lifetime control based on `Group`."""
  
      @property
      @abc.abstractmethod
      def async_group(self) -> Group:
          """Group controlling resource's lifetime."""
  
      @property
      def is_open(self) -> bool:
          """``True`` if not closing or closed, ``False`` otherwise."""
  
      @property
      def is_closing(self) -> bool:
          """Is resource closing or closed."""
  
      @property
      def is_closed(self) -> bool:
          """Is resource closed."""
  
      async def wait_closing(self):
          """Wait until closing is ``True``."""
  
      async def wait_closed(self):
          """Wait until closed is ``True``."""
  
      def close(self):
          """Close resource."""
  
      async def async_close(self):
          """Close resource and wait until closed is ``True``."""