API reference

Event loop

anyio.run(func, *args, backend='asyncio', backend_options=None)

Run the given coroutine function in an asynchronous event loop.

The current thread must not be already running an event loop.

Parameters
  • func (Callable[…, Coroutine[Any, Any, ~T_Retval]]) – a coroutine function

  • args (object) – positional arguments to func

  • backend (str) – name of the asynchronous event loop implementation – currently either asyncio or trio

  • backend_options (Optional[Dict[str, Any]]) – keyword arguments to call the backend run() implementation with (documented here)

Return type

~T_Retval

Returns

the return value of the coroutine function

Raises
  • RuntimeError – if an asynchronous event loop is already running in this thread

  • LookupError – if the named backend is not found

anyio.get_all_backends()

Return a tuple of the names of all built-in backends.

Return type

Tuple[str, …]

anyio.get_cancelled_exc_class()

Return the current async library’s cancellation exception class.

Return type

Type[BaseException]

async anyio.sleep(delay)

Pause the current task for the specified duration.

Parameters

delay (float) – the duration, in seconds

Return type

None

async anyio.sleep_forever()

Pause the current task until it’s cancelled.

This is a shortcut for sleep(math.inf).

New in version 3.1.

Return type

None

async anyio.sleep_until(deadline)

Pause the current task until the given time.

Parameters

deadline (float) – the absolute time to wake up at (according to the internal monotonic clock of the event loop)

New in version 3.1.

Return type

None

anyio.current_time()

Return the current value of the event loop’s internal clock.

Return type

DeprecatedAwaitableFloat

Returns

the clock value (seconds)

Asynchronous resources

async anyio.aclose_forcefully(resource)

Close an asynchronous resource in a cancelled scope.

Doing this closes the resource without waiting on anything.

Parameters

resource (AsyncResource) – the resource to close

Return type

None

class anyio.abc.AsyncResource

Bases: object

Abstract base class for all closeable asynchronous resources.

Works as an asynchronous context manager which returns the instance itself on enter, and calls aclose() on exit.

abstract async aclose()

Close the resource.

Return type

None

Typed attributes

anyio.typed_attribute()

Return a unique object, used to mark typed attributes.

Return type

Any

class anyio.TypedAttributeSet

Bases: object

Superclass for typed attribute collections.

Checks that every public attribute of every subclass has a type annotation.

class anyio.TypedAttributeProvider

Bases: object

Base class for classes that wish to provide typed extra attributes.

extra(attribute, default=<object object>)

Return the value of the given typed extra attribute.

Parameters
  • attribute (Any) – the attribute (member of a TypedAttributeSet) to look for

  • default (object) – the value that should be returned if no value is found for the attribute

Raises

TypedAttributeLookupError – if the search failed and no default value was given

Return type

object

property extra_attributes: Mapping[T_Attr, Callable[T_Attr]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[~T_Attr, Callable[[], ~T_Attr]]

Timeouts and cancellation

anyio.open_cancel_scope(*, shield=False)

Open a cancel scope.

Parameters

shield (bool) – True to shield the cancel scope from external cancellation

Return type

CancelScope

Returns

a cancel scope

Deprecated since version 3.0: Use CancelScope directly.

anyio.move_on_after(delay, shield=False)

Create a cancel scope with a deadline that expires after the given delay.

Parameters
  • delay (Optional[float]) – maximum allowed time (in seconds) before exiting the context block, or None to disable the timeout

  • shield (bool) – True to shield the cancel scope from external cancellation

Return type

CancelScope

Returns

a cancel scope

anyio.fail_after(delay, shield=False)

Create a context manager which raises a TimeoutError if does not finish in time.

Parameters
  • delay (Optional[float]) – maximum allowed time (in seconds) before raising the exception, or None to disable the timeout

  • shield (bool) – True to shield the cancel scope from external cancellation

Returns

a context manager that yields a cancel scope

Return type

ContextManager[CancelScope]

anyio.current_effective_deadline()

Return the nearest deadline among all the cancel scopes effective for the current task.

Returns

a clock value from the event loop’s internal clock (float('inf') if there is no deadline in effect)

Return type

float

class anyio.CancelScope(*, deadline: float = inf, shield: bool = False)

Bases: anyio._core._compat.DeprecatedAsyncContextManager[CancelScope]

Wraps a unit of work that can be made separately cancellable.

Parameters
  • deadline – The time (clock value) when this scope is cancelled automatically

  • shieldTrue to shield the cancel scope from external cancellation

cancel()

Cancel this scope immediately.

Return type

DeprecatedAwaitable

property cancel_called: bool

True if cancel() has been called.

Return type

bool

property deadline: float

The time (clock value) when this scope is cancelled automatically.

Will be float('inf') if no timeout has been set.

Return type

float

property shield: bool

True if this scope is shielded from external cancellation.

While a scope is shielded, it will not receive cancellations from outside.

Return type

bool

Task groups

anyio.create_task_group()

Create a task group.

Return type

TaskGroup

Returns

a task group

class anyio.abc.TaskGroup

Bases: object

Groups several asynchronous tasks together.

Variables

cancel_scope (CancelScope) – the cancel scope inherited by all child tasks

async spawn(func, *args, name=None)

Start a new task in this task group.

Parameters
  • func (Callable[…, Coroutine]) – a coroutine function

  • args (object) – positional arguments to call the function with

  • name (object) – name of the task, for the purposes of introspection and debugging

Deprecated since version 3.0: Use start_soon() instead. If your code needs AnyIO 2 compatibility, you can keep using this until AnyIO 4.

Return type

None

abstract async start(func, *args, name=None)

Start a new task and wait until it signals for readiness.

Parameters
  • func (Callable[…, Coroutine]) – a coroutine function

  • args (object) – positional arguments to call the function with

  • name (object) – name of the task, for the purposes of introspection and debugging

Return type

object

Returns

the value passed to task_status.started()

Raises

RuntimeError – if the task finishes without calling task_status.started()

New in version 3.0.

abstract start_soon(func, *args, name=None)

Start a new task in this task group.

Parameters
  • func (Callable[…, Coroutine]) – a coroutine function

  • args (object) – positional arguments to call the function with

  • name (object) – name of the task, for the purposes of introspection and debugging

New in version 3.0.

Return type

None

class anyio.abc.TaskStatus

Bases: object

abstract started(value=None)

Signal that the task has started.

Parameters

value (object) – object passed back to the starter of the task

Return type

None

Running code in worker threads

async anyio.to_thread.run_sync(func, *args, cancellable=False, limiter=None)

Call the given function with the given arguments in a worker thread.

If the cancellable option is enabled and the task waiting for its completion is cancelled, the thread will still run its course but its return value (or any raised exception) will be ignored.

Parameters
  • func (Callable[…, ~T_Retval]) – a callable

  • args (object) – positional arguments for the callable

  • cancellable (bool) – True to allow cancellation of the operation

  • limiter (Optional[CapacityLimiter]) – capacity limiter to use to limit the total amount of threads running (if omitted, the default limiter is used)

Return type

~T_Retval

Returns

an awaitable that yields the return value of the function.

anyio.to_thread.current_default_thread_limiter()

Return the capacity limiter that is used by default to limit the number of concurrent threads.

Return type

CapacityLimiter

Returns

a capacity limiter object

Running code in worker processes

async anyio.to_process.run_sync(func, *args, cancellable=False, limiter=None)

Call the given function with the given arguments in a worker process.

If the cancellable option is enabled and the task waiting for its completion is cancelled, the worker process running it will be abruptly terminated using SIGKILL (or terminateProcess() on Windows).

Parameters
  • func (Callable[…, ~T_Retval]) – a callable

  • args (object) – positional arguments for the callable

  • cancellable (bool) – True to allow cancellation of the operation while it’s running

  • limiter (Optional[CapacityLimiter]) – capacity limiter to use to limit the total amount of processes running (if omitted, the default limiter is used)

Return type

~T_Retval

Returns

an awaitable that yields the return value of the function.

anyio.to_process.current_default_process_limiter()

Return the capacity limiter that is used by default to limit the number of worker processes.

Return type

CapacityLimiter

Returns

a capacity limiter object

Running asynchronous code from other threads

anyio.from_thread.run(func, *args)

Call a coroutine function from a worker thread.

Parameters
Return type

~T_Retval

Returns

the return value of the coroutine function

anyio.from_thread.run_sync(func, *args)

Call a function in the event loop thread from a worker thread.

Parameters
  • func (Callable[…, ~T_Retval]) – a callable

  • args (object) – positional arguments for the callable

Return type

~T_Retval

Returns

the return value of the callable

anyio.from_thread.create_blocking_portal()

Create a portal for running functions in the event loop thread from external threads.

Use this function in asynchronous code when you need to allow external threads access to the event loop where your asynchronous code is currently running.

Deprecated since version 3.0: Use BlockingPortal directly.

Return type

BlockingPortal

anyio.from_thread.start_blocking_portal(backend='asyncio', backend_options=None)

Start a new event loop in a new thread and run a blocking portal in its main task.

The parameters are the same as for run().

Parameters
Return type

Generator[BlockingPortal, Any, None]

Returns

a context manager that yields a blocking portal

Changed in version 3.0: Usage as a context manager is now required.

class anyio.abc.BlockingPortal

Bases: object

An object that lets external threads run code in an asynchronous event loop.

call(func: Callable[..., Coroutine[[Any, Any], T_Retval]], *args: object) T_Retval
call(func: Callable[..., T_Retval], *args: object) T_Retval

Call the given function in the event loop thread.

If the callable returns a coroutine object, it is awaited on.

Parameters

func (Callable[…, Union[Coroutine[Any, Any, ~T_Retval], ~T_Retval]]) – any callable

Raises

RuntimeError – if the portal is not running or if this method is called from within the event loop thread

Return type

~T_Retval

async sleep_until_stopped()

Sleep until stop() is called.

Return type

None

spawn_task(func: Callable[..., Coroutine[[Any, Any], T_Retval]], *args: object, name: object = 'None') Future[T_Retval]
spawn_task(func: Callable[..., T_Retval], *args: object, name: object = 'None') Future[T_Retval]

Start a task in the portal’s task group.

Parameters
  • func – the target coroutine function

  • args – positional arguments passed to func

  • name – name of the task (will be coerced to a string if not None)

Returns

a future that resolves with the return value of the callable if the task completes successfully, or with the exception raised in the task

Raises

RuntimeError – if the portal is not running or if this method is called from within the event loop thread

New in version 2.1.

Deprecated since version 3.0: Use start_task_soon() instead. If your code needs AnyIO 2 compatibility, you can keep using this until AnyIO 4.

start_task(func, *args, name=None)

Start a task in the portal’s task group and wait until it signals for readiness.

This method works the same way as TaskGroup.start().

Parameters
  • func (Callable[…, Coroutine]) – the target coroutine function

  • args (object) – positional arguments passed to func

  • name (object) – name of the task (will be coerced to a string if not None)

Return type

Tuple[Future, Any]

Returns

a tuple of (future, task_status_value) where the task_status_value is the value passed to task_status.started() from within the target function

New in version 3.0.

start_task_soon(func: Callable[..., Coroutine[[Any, Any], T_Retval]], *args: object, name: object = 'None') Future[T_Retval]
start_task_soon(func: Callable[..., T_Retval], *args: object, name: object = 'None') Future[T_Retval]

Start a task in the portal’s task group.

The task will be run inside a cancel scope which can be cancelled by cancelling the returned future.

Parameters
  • func – the target coroutine function

  • args – positional arguments passed to func

  • name – name of the task (will be coerced to a string if not None)

Returns

a future that resolves with the return value of the callable if the task completes successfully, or with the exception raised in the task

Raises

RuntimeError – if the portal is not running or if this method is called from within the event loop thread

New in version 3.0.

async stop(cancel_remaining=False)

Signal the portal to shut down.

This marks the portal as no longer accepting new calls and exits from sleep_until_stopped().

Parameters

cancel_remaining (bool) – True to cancel all the remaining tasks, False to let them finish before returning

Return type

None

wrap_async_context_manager(cm)

Wrap an async context manager as a synchronous context manager via this portal.

Spawns a task that will call both __aenter__() and __aexit__(), stopping in the middle until the synchronous context manager exits.

Parameters

cm (AsyncContextManager[~T_co]) – an asynchronous context manager

Return type

ContextManager[~T_co]

Returns

a synchronous context manager

New in version 2.1.

Async file I/O

async anyio.open_file(file, mode='r', buffering=- 1, encoding=None, errors=None, newline=None, closefd=True, opener=None)

Open a file asynchronously.

The arguments are exactly the same as for the builtin open().

Return type

AsyncFile

Returns

an asynchronous file object

anyio.wrap_file(file)

Wrap an existing file as an asynchronous file.

Parameters

file (IO[AnyStr]) – an existing file-like object

Return type

AsyncFile[AnyStr]

Returns

an asynchronous file object

class anyio.AsyncFile(fp)

Bases: anyio.abc.AsyncResource, Generic[AnyStr]

An asynchronous file object.

This class wraps a standard file object and provides async friendly versions of the following blocking methods (where available on the original file object):

  • read

  • read1

  • readline

  • readlines

  • readinto

  • readinto1

  • write

  • writelines

  • truncate

  • seek

  • tell

  • flush

All other methods are directly passed through.

This class supports the asynchronous context manager protocol which closes the underlying file at the end of the context block.

This class also supports asynchronous iteration:

async with await open_file(...) as f:
    async for line in f:
        print(line)
async aclose()

Close the resource.

Return type

None

property wrapped: IO[AnyStr]

The wrapped file object.

Return type

IO[AnyStr]

class anyio.Path(*args)

Bases: object

An asynchronous version of pathlib.Path.

This class cannot be substituted for pathlib.Path or pathlib.PurePath, but it is compatible with the os.PathLike interface.

It implements the Python 3.10 version of pathlib.Path interface, except for the deprecated link_to() method.

Any methods that do disk I/O need to be awaited on. These methods are:

Additionally, the following methods return an async iterator yielding Path objects:

Streams and stream wrappers

anyio.create_memory_object_stream(max_buffer_size=0, item_type=None)

Create a memory object stream.

Parameters
  • max_buffer_size (float) – number of items held in the buffer until send() starts blocking

  • item_type (Optional[Type[~T_Item]]) – type of item, for marking the streams with the right generic type for static typing (not used at run time)

Return type

Tuple[MemoryObjectSendStream, MemoryObjectReceiveStream]

Returns

a tuple of (send stream, receive stream)

class anyio.abc.UnreliableObjectReceiveStream

Bases: Generic[T_Item], anyio.abc.AsyncResource, anyio.TypedAttributeProvider

An interface for receiving objects.

This interface makes no guarantees that the received messages arrive in the order in which they were sent, or that no messages are missed.

Asynchronously iterating over objects of this type will yield objects matching the given type parameter.

abstract async receive()

Receive the next item.

Raises
Return type

~T_Item

class anyio.abc.UnreliableObjectSendStream

Bases: Generic[T_Item], anyio.abc.AsyncResource, anyio.TypedAttributeProvider

An interface for sending objects.

This interface makes no guarantees that the messages sent will reach the recipient(s) in the same order in which they were sent, or at all.

abstract async send(item)

Send an item to the peer(s).

Parameters

item (~T_Item) – the item to send

Raises
Return type

None

class anyio.abc.UnreliableObjectStream

Bases: anyio.abc._streams.UnreliableObjectReceiveStream[T_Item], anyio.abc._streams.UnreliableObjectSendStream[T_Item]

A bidirectional message stream which does not guarantee the order or reliability of message delivery.

class anyio.abc.ObjectReceiveStream

Bases: anyio.abc._streams.UnreliableObjectReceiveStream[T_Item]

A receive message stream which guarantees that messages are received in the same order in which they were sent, and that no messages are missed.

class anyio.abc.ObjectSendStream

Bases: anyio.abc._streams.UnreliableObjectSendStream[T_Item]

A send message stream which guarantees that messages are delivered in the same order in which they were sent, without missing any messages in the middle.

class anyio.abc.ObjectStream

Bases: anyio.abc._streams.ObjectReceiveStream[T_Item], anyio.abc._streams.ObjectSendStream[T_Item], anyio.abc._streams.UnreliableObjectStream[T_Item]

A bidirectional message stream which guarantees the order and reliability of message delivery.

abstract async send_eof()

Send an end-of-file indication to the peer.

You should not try to send any further data to this stream after calling this method. This method is idempotent (does nothing on successive calls).

Return type

None

class anyio.abc.ByteReceiveStream

Bases: anyio.abc.AsyncResource, anyio.TypedAttributeProvider

An interface for receiving bytes from a single peer.

Iterating this byte stream will yield a byte string of arbitrary length, but no more than 65536 bytes.

abstract async receive(max_bytes=65536)

Receive at most max_bytes bytes from the peer.

Note

Implementors of this interface should not return an empty bytes object, and users should ignore them.

Parameters

max_bytes (int) – maximum number of bytes to receive

Return type

bytes

Returns

the received bytes

Raises

EndOfStream – if this stream has been closed from the other end

class anyio.abc.ByteSendStream

Bases: anyio.abc.AsyncResource, anyio.TypedAttributeProvider

An interface for sending bytes to a single peer.

abstract async send(item)

Send the given bytes to the peer.

Parameters

item (bytes) – the bytes to send

Return type

None

class anyio.abc.ByteStream

Bases: anyio.abc.ByteReceiveStream, anyio.abc.ByteSendStream

A bidirectional byte stream.

abstract async send_eof()

Send an end-of-file indication to the peer.

You should not try to send any further data to this stream after calling this method. This method is idempotent (does nothing on successive calls).

Return type

None

class anyio.abc.Listener(*args, **kwds)

Bases: Generic[T_Stream], anyio.abc.AsyncResource, anyio.TypedAttributeProvider

An interface for objects that let you accept incoming connections.

abstract async serve(handler, task_group=None)

Accept incoming connections as they come in and start tasks to handle them.

Parameters
  • handler (Callable[[~T_Stream], Any]) – a callable that will be used to handle each accepted connection

  • task_group (Optional[TaskGroup]) – the task group that will be used to start tasks for handling each accepted connection (if omitted, an ad-hoc task group will be created)

Return type

None

anyio.abc.AnyUnreliableByteReceiveStream = typing.Union[anyio.abc.UnreliableObjectReceiveStream[bytes], anyio.abc.ByteReceiveStream]

Union type; Union[X, Y] means either X or Y.

To define a union, use e.g. Union[int, str]. Details:

  • The arguments must be types and there must be at least one.

  • None as an argument is a special case and is replaced by type(None).

  • Unions of unions are flattened, e.g.:

    Union[Union[int, str], float] == Union[int, str, float]
    
  • Unions of a single argument vanish, e.g.:

    Union[int] == int  # The constructor actually returns int
    
  • Redundant arguments are skipped, e.g.:

    Union[int, str, int] == Union[int, str]
    
  • When comparing unions, the argument order is ignored, e.g.:

    Union[int, str] == Union[str, int]
    
  • When two arguments have a subclass relationship, the least derived argument is kept, e.g.:

    class Employee: pass
    class Manager(Employee): pass
    Union[int, Employee, Manager] == Union[int, Employee]
    Union[Manager, int, Employee] == Union[int, Employee]
    Union[Employee, Manager] == Employee
    
  • Similar for object:

    Union[int, object] == object
    
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].

anyio.abc.AnyUnreliableByteSendStream = typing.Union[anyio.abc.UnreliableObjectSendStream[bytes], anyio.abc.ByteSendStream]

Union type; Union[X, Y] means either X or Y.

To define a union, use e.g. Union[int, str]. Details:

  • The arguments must be types and there must be at least one.

  • None as an argument is a special case and is replaced by type(None).

  • Unions of unions are flattened, e.g.:

    Union[Union[int, str], float] == Union[int, str, float]
    
  • Unions of a single argument vanish, e.g.:

    Union[int] == int  # The constructor actually returns int
    
  • Redundant arguments are skipped, e.g.:

    Union[int, str, int] == Union[int, str]
    
  • When comparing unions, the argument order is ignored, e.g.:

    Union[int, str] == Union[str, int]
    
  • When two arguments have a subclass relationship, the least derived argument is kept, e.g.:

    class Employee: pass
    class Manager(Employee): pass
    Union[int, Employee, Manager] == Union[int, Employee]
    Union[Manager, int, Employee] == Union[int, Employee]
    Union[Employee, Manager] == Employee
    
  • Similar for object:

    Union[int, object] == object
    
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].

anyio.abc.AnyUnreliableByteStream = typing.Union[anyio.abc.UnreliableObjectStream[bytes], anyio.abc.ByteStream]

Union type; Union[X, Y] means either X or Y.

To define a union, use e.g. Union[int, str]. Details:

  • The arguments must be types and there must be at least one.

  • None as an argument is a special case and is replaced by type(None).

  • Unions of unions are flattened, e.g.:

    Union[Union[int, str], float] == Union[int, str, float]
    
  • Unions of a single argument vanish, e.g.:

    Union[int] == int  # The constructor actually returns int
    
  • Redundant arguments are skipped, e.g.:

    Union[int, str, int] == Union[int, str]
    
  • When comparing unions, the argument order is ignored, e.g.:

    Union[int, str] == Union[str, int]
    
  • When two arguments have a subclass relationship, the least derived argument is kept, e.g.:

    class Employee: pass
    class Manager(Employee): pass
    Union[int, Employee, Manager] == Union[int, Employee]
    Union[Manager, int, Employee] == Union[int, Employee]
    Union[Employee, Manager] == Employee
    
  • Similar for object:

    Union[int, object] == object
    
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].

anyio.abc.AnyByteReceiveStream = typing.Union[anyio.abc.ObjectReceiveStream[bytes], anyio.abc.ByteReceiveStream]

Union type; Union[X, Y] means either X or Y.

To define a union, use e.g. Union[int, str]. Details:

  • The arguments must be types and there must be at least one.

  • None as an argument is a special case and is replaced by type(None).

  • Unions of unions are flattened, e.g.:

    Union[Union[int, str], float] == Union[int, str, float]
    
  • Unions of a single argument vanish, e.g.:

    Union[int] == int  # The constructor actually returns int
    
  • Redundant arguments are skipped, e.g.:

    Union[int, str, int] == Union[int, str]
    
  • When comparing unions, the argument order is ignored, e.g.:

    Union[int, str] == Union[str, int]
    
  • When two arguments have a subclass relationship, the least derived argument is kept, e.g.:

    class Employee: pass
    class Manager(Employee): pass
    Union[int, Employee, Manager] == Union[int, Employee]
    Union[Manager, int, Employee] == Union[int, Employee]
    Union[Employee, Manager] == Employee
    
  • Similar for object:

    Union[int, object] == object
    
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].

anyio.abc.AnyByteSendStream = typing.Union[anyio.abc.ObjectSendStream[bytes], anyio.abc.ByteSendStream]

Union type; Union[X, Y] means either X or Y.

To define a union, use e.g. Union[int, str]. Details:

  • The arguments must be types and there must be at least one.

  • None as an argument is a special case and is replaced by type(None).

  • Unions of unions are flattened, e.g.:

    Union[Union[int, str], float] == Union[int, str, float]
    
  • Unions of a single argument vanish, e.g.:

    Union[int] == int  # The constructor actually returns int
    
  • Redundant arguments are skipped, e.g.:

    Union[int, str, int] == Union[int, str]
    
  • When comparing unions, the argument order is ignored, e.g.:

    Union[int, str] == Union[str, int]
    
  • When two arguments have a subclass relationship, the least derived argument is kept, e.g.:

    class Employee: pass
    class Manager(Employee): pass
    Union[int, Employee, Manager] == Union[int, Employee]
    Union[Manager, int, Employee] == Union[int, Employee]
    Union[Employee, Manager] == Employee
    
  • Similar for object:

    Union[int, object] == object
    
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].

anyio.abc.AnyByteStream = typing.Union[anyio.abc.ObjectStream[bytes], anyio.abc.ByteStream]

Union type; Union[X, Y] means either X or Y.

To define a union, use e.g. Union[int, str]. Details:

  • The arguments must be types and there must be at least one.

  • None as an argument is a special case and is replaced by type(None).

  • Unions of unions are flattened, e.g.:

    Union[Union[int, str], float] == Union[int, str, float]
    
  • Unions of a single argument vanish, e.g.:

    Union[int] == int  # The constructor actually returns int
    
  • Redundant arguments are skipped, e.g.:

    Union[int, str, int] == Union[int, str]
    
  • When comparing unions, the argument order is ignored, e.g.:

    Union[int, str] == Union[str, int]
    
  • When two arguments have a subclass relationship, the least derived argument is kept, e.g.:

    class Employee: pass
    class Manager(Employee): pass
    Union[int, Employee, Manager] == Union[int, Employee]
    Union[Manager, int, Employee] == Union[int, Employee]
    Union[Employee, Manager] == Employee
    
  • Similar for object:

    Union[int, object] == object
    
  • You cannot subclass or instantiate a union.

  • You can use Optional[X] as a shorthand for Union[X, None].

class anyio.streams.buffered.BufferedByteReceiveStream(receive_stream)

Bases: anyio.abc.ByteReceiveStream

Wraps any bytes-based receive stream and uses a buffer to provide sophisticated receiving capabilities in the form of a byte stream.

async aclose()

Close the resource.

Return type

None

property buffer: bytes

The bytes currently in the buffer.

Return type

bytes

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async receive(max_bytes=65536)

Receive at most max_bytes bytes from the peer.

Note

Implementors of this interface should not return an empty bytes object, and users should ignore them.

Parameters

max_bytes (int) – maximum number of bytes to receive

Return type

bytes

Returns

the received bytes

Raises

EndOfStream – if this stream has been closed from the other end

async receive_exactly(nbytes)

Read exactly the given amount of bytes from the stream.

Parameters

nbytes (int) – the number of bytes to read

Return type

bytes

Returns

the bytes read

Raises

IncompleteRead – if the stream was closed before the requested amount of bytes could be read from the stream

async receive_until(delimiter, max_bytes)

Read from the stream until the delimiter is found or max_bytes have been read.

Parameters
  • delimiter (bytes) – the marker to look for in the stream

  • max_bytes (int) – maximum number of bytes that will be read before raising DelimiterNotFound

Return type

bytes

Returns

the bytes read (not including the delimiter)

Raises
  • IncompleteRead – if the stream was closed before the delimiter was found

  • DelimiterNotFound – if the delimiter is not found within the bytes read up to the maximum allowed

class anyio.streams.file.FileStreamAttribute

Bases: anyio.TypedAttributeSet

file: BinaryIO = <object object>

the open file descriptor

fileno: int = <object object>

the file number, if available (file must be a real file or a TTY)

path: pathlib.Path = <object object>

the path of the file on the file system, if available (file must be a real file)

class anyio.streams.file.FileReadStream(file)

Bases: anyio.streams.file._BaseFileStream, anyio.abc.ByteReceiveStream

A byte stream that reads from a file in the file system.

Parameters

file (BinaryIO) – a file that has been opened for reading in binary mode

New in version 3.0.

async classmethod from_path(path)

Create a file read stream by opening the given file.

Parameters

path (Union[str, PathLike]) – path of the file to read from

Return type

FileReadStream

async receive(max_bytes=65536)

Receive at most max_bytes bytes from the peer.

Note

Implementors of this interface should not return an empty bytes object, and users should ignore them.

Parameters

max_bytes (int) – maximum number of bytes to receive

Return type

bytes

Returns

the received bytes

Raises

EndOfStream – if this stream has been closed from the other end

async seek(position, whence=0)

Seek the file to the given position.

See also

io.IOBase.seek()

Note

Not all file descriptors are seekable.

Parameters
  • position (int) – position to seek the file to

  • whence (int) – controls how position is interpreted

Return type

int

Returns

the new absolute position

Raises

OSError – if the file is not seekable

async tell()

Return the current stream position.

Note

Not all file descriptors are seekable.

Return type

int

Returns

the current absolute position

Raises

OSError – if the file is not seekable

class anyio.streams.file.FileWriteStream(file)

Bases: anyio.streams.file._BaseFileStream, anyio.abc.ByteSendStream

A byte stream that writes to a file in the file system.

Parameters

file (BinaryIO) – a file that has been opened for writing in binary mode

New in version 3.0.

async classmethod from_path(path, append=False)

Create a file write stream by opening the given file for writing.

Parameters
  • path (Union[str, PathLike]) – path of the file to write to

  • append (bool) – if True, open the file for appending; if False, any existing file at the given path will be truncated

Return type

FileWriteStream

async send(item)

Send the given bytes to the peer.

Parameters

item (bytes) – the bytes to send

Return type

None

class anyio.streams.memory.MemoryObjectReceiveStream(_state)

Bases: Generic[T_Item], anyio.abc.ObjectReceiveStream[T_Item]

async aclose()

Close the resource.

Return type

None

clone()

Create a clone of this receive stream.

Each clone can be closed separately. Only when all clones have been closed will the receiving end of the memory stream be considered closed by the sending ends.

Return type

MemoryObjectReceiveStream

Returns

the cloned stream

close()

Close the stream.

This works the exact same way as aclose(), but is provided as a special case for the benefit of synchronous callbacks.

Return type

None

async receive()

Receive the next item.

Raises
Return type

~T_Item

receive_nowait()

Receive the next item if it can be done without waiting.

Return type

~T_Item

Returns

the received item

Raises
  • ClosedResourceError – if this send stream has been closed

  • EndOfStream – if the buffer is empty and this stream has been closed from the sending end

  • WouldBlock – if there are no items in the buffer and no tasks waiting to send

statistics()

Return statistics about the current state of this stream.

New in version 3.0.

Return type

MemoryObjectStreamStatistics

class anyio.streams.memory.MemoryObjectSendStream(_state)

Bases: Generic[T_Item], anyio.abc.ObjectSendStream[T_Item]

async aclose()

Close the resource.

Return type

None

clone()

Create a clone of this send stream.

Each clone can be closed separately. Only when all clones have been closed will the sending end of the memory stream be considered closed by the receiving ends.

Return type

MemoryObjectSendStream

Returns

the cloned stream

close()

Close the stream.

This works the exact same way as aclose(), but is provided as a special case for the benefit of synchronous callbacks.

Return type

None

async send(item)

Send an item to the peer(s).

Parameters

item (~T_Item) – the item to send

Raises
Return type

None

send_nowait(item)

Send an item immediately if it can be done without waiting.

Parameters

item (~T_Item) – the item to send

Raises
Return type

DeprecatedAwaitable

statistics()

Return statistics about the current state of this stream.

New in version 3.0.

Return type

MemoryObjectStreamStatistics

class anyio.streams.memory.MemoryObjectStreamStatistics(current_buffer_used, max_buffer_size, open_send_streams, open_receive_streams, tasks_waiting_send, tasks_waiting_receive)

Bases: tuple

property current_buffer_used

number of items stored in the buffer

property max_buffer_size

maximum number of items that can be stored on this stream (or math.inf)

property open_receive_streams

number of unclosed clones of the receive stream

property open_send_streams

number of unclosed clones of the send stream

property tasks_waiting_receive

number of tasks blocked on MemoryObjectReceiveStream.receive()

property tasks_waiting_send

number of tasks blocked on MemoryObjectSendStream.send()

class anyio.streams.stapled.MultiListener(listeners)

Bases: Generic[T_Stream], anyio.abc.Listener[T_Stream]

Combines multiple listeners into one, serving connections from all of them at once.

Any MultiListeners in the given collection of listeners will have their listeners moved into this one.

Extra attributes are provided from each listener, with each successive listener overriding any conflicting attributes from the previous one.

Parameters

listeners (Sequence[Listener[T_Stream]]) – listeners to serve

async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async serve(handler, task_group=None)

Accept incoming connections as they come in and start tasks to handle them.

Parameters
  • handler (Callable[[~T_Stream], Any]) – a callable that will be used to handle each accepted connection

  • task_group (Optional[TaskGroup]) – the task group that will be used to start tasks for handling each accepted connection (if omitted, an ad-hoc task group will be created)

Return type

None

class anyio.streams.stapled.StapledByteStream(send_stream, receive_stream)

Bases: anyio.abc.ByteStream

Combines two byte streams into a single, bidirectional byte stream.

Extra attributes will be provided from both streams, with the receive stream providing the values in case of a conflict.

Parameters
async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async receive(max_bytes=65536)

Receive at most max_bytes bytes from the peer.

Note

Implementors of this interface should not return an empty bytes object, and users should ignore them.

Parameters

max_bytes (int) – maximum number of bytes to receive

Return type

bytes

Returns

the received bytes

Raises

EndOfStream – if this stream has been closed from the other end

async send(item)

Send the given bytes to the peer.

Parameters

item (bytes) – the bytes to send

Return type

None

async send_eof()

Send an end-of-file indication to the peer.

You should not try to send any further data to this stream after calling this method. This method is idempotent (does nothing on successive calls).

Return type

None

class anyio.streams.stapled.StapledObjectStream(send_stream, receive_stream)

Bases: Generic[T_Item], anyio.abc.ObjectStream[T_Item]

Combines two object streams into a single, bidirectional object stream.

Extra attributes will be provided from both streams, with the receive stream providing the values in case of a conflict.

Parameters
async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async receive()

Receive the next item.

Raises
Return type

~T_Item

async send(item)

Send an item to the peer(s).

Parameters

item (~T_Item) – the item to send

Raises
Return type

None

async send_eof()

Send an end-of-file indication to the peer.

You should not try to send any further data to this stream after calling this method. This method is idempotent (does nothing on successive calls).

Return type

None

class anyio.streams.text.TextReceiveStream(transport_stream, encoding='utf-8', errors='strict')

Bases: anyio.abc.ObjectReceiveStream[str]

Stream wrapper that decodes bytes to strings using the given encoding.

Decoding is done using IncrementalDecoder which returns any completely received unicode characters as soon as they come in.

Parameters
  • transport_stream (Union[ObjectReceiveStream[bytes], ByteReceiveStream]) – any bytes-based receive stream

  • encoding (InitVar) – character encoding to use for decoding bytes to strings (defaults to utf-8)

  • errors (InitVar) – handling scheme for decoding errors (defaults to strict; see the codecs module documentation for a comprehensive list of options)

async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async receive()

Receive the next item.

Raises
Return type

str

class anyio.streams.text.TextSendStream(transport_stream, encoding='utf-8', errors='strict')

Bases: anyio.abc.ObjectSendStream[str]

Sends strings to the wrapped stream as bytes using the given encoding.

Parameters
  • transport_stream (AnyByteSendStream) – any bytes-based send stream

  • encoding (str) – character encoding to use for encoding strings to bytes (defaults to utf-8)

  • errors (str) – handling scheme for encoding errors (defaults to strict; see the codecs module documentation for a comprehensive list of options)

async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async send(item)

Send an item to the peer(s).

Parameters

item (str) – the item to send

Raises
Return type

None

class anyio.streams.text.TextStream(transport_stream, encoding='utf-8', errors='strict')

Bases: anyio.abc.ObjectStream[str]

A bidirectional stream that decodes bytes to strings on receive and encodes strings to bytes on send.

Extra attributes will be provided from both streams, with the receive stream providing the values in case of a conflict.

Parameters
  • transport_stream (AnyByteStream) – any bytes-based stream

  • encoding (str) – character encoding to use for encoding/decoding strings to/from bytes (defaults to utf-8)

  • errors (str) – handling scheme for encoding errors (defaults to strict; see the codecs module documentation for a comprehensive list of options)

async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async receive()

Receive the next item.

Raises
Return type

str

async send(item)

Send an item to the peer(s).

Parameters

item (str) – the item to send

Raises
Return type

None

async send_eof()

Send an end-of-file indication to the peer.

You should not try to send any further data to this stream after calling this method. This method is idempotent (does nothing on successive calls).

Return type

None

class anyio.streams.tls.TLSAttribute

Bases: anyio.TypedAttributeSet

Contains Transport Layer Security related attributes.

alpn_protocol: Optional[str] = <object object>

the selected ALPN protocol

channel_binding_tls_unique: bytes = <object object>

the channel binding for type tls-unique

cipher: Tuple[str, str, int] = <object object>

the selected cipher

peer_certificate: Optional[Dict[str, Union[str, tuple]]] = <object object>

the peer certificate in dictionary form (see ssl.SSLSocket.getpeercert() for more information)

peer_certificate_binary: Optional[bytes] = <object object>

the peer certificate in binary form

server_side: bool = <object object>

True if this is the server side of the connection

shared_ciphers: List[Tuple[str, str, int]] = <object object>

ciphers shared between both ends of the TLS connection

ssl_object: ssl.SSLObject = <object object>

the SSLObject used for encryption

standard_compatible: bool = <object object>

True if this stream does (and expects) a closing TLS handshake when the stream is being closed

tls_version: str = <object object>

the TLS protocol version (e.g. TLSv1.2)

class anyio.streams.tls.TLSStream(transport_stream, standard_compatible, _ssl_object, _read_bio, _write_bio)

Bases: anyio.abc.ByteStream

A stream wrapper that encrypts all sent data and decrypts received data.

This class has no public initializer; use wrap() instead. All extra attributes from TLSAttribute are supported.

Variables

transport_stream (AnyByteStream) – the wrapped stream

async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async receive(max_bytes=65536)

Receive at most max_bytes bytes from the peer.

Note

Implementors of this interface should not return an empty bytes object, and users should ignore them.

Parameters

max_bytes (int) – maximum number of bytes to receive

Return type

bytes

Returns

the received bytes

Raises

EndOfStream – if this stream has been closed from the other end

async send(item)

Send the given bytes to the peer.

Parameters

item (bytes) – the bytes to send

Return type

None

async send_eof()

Send an end-of-file indication to the peer.

You should not try to send any further data to this stream after calling this method. This method is idempotent (does nothing on successive calls).

Return type

None

async unwrap()

Does the TLS closing handshake.

Return type

Tuple[Union[ObjectStream[bytes], ByteStream], bytes]

Returns

a tuple of (wrapped byte stream, bytes left in the read buffer)

async classmethod wrap(transport_stream, *, server_side=None, hostname=None, ssl_context=None, standard_compatible=True)

Wrap an existing stream with Transport Layer Security.

This performs a TLS handshake with the peer.

Parameters
  • transport_stream (Union[ObjectStream[bytes], ByteStream]) – a bytes-transporting stream to wrap

  • server_side (Optional[bool]) – True if this is the server side of the connection, False if this is the client side (if omitted, will be set to False if hostname has been provided, False otherwise). Used only to create a default context when an explicit context has not been provided.

  • hostname (Optional[str]) – host name of the peer (if host name checking is desired)

  • ssl_context (Optional[SSLContext]) – the SSLContext object to use (if not provided, a secure default will be created)

  • standard_compatible (bool) – if False, skip the closing handshake when closing the connection, and don’t raise an exception if the peer does the same

Raises

SSLError – if the TLS handshake fails

Return type

TLSStream

class anyio.streams.tls.TLSListener(listener, ssl_context, standard_compatible=True, handshake_timeout=30)

Bases: anyio.abc.Listener[anyio.streams.tls.TLSStream]

A convenience listener that wraps another listener and auto-negotiates a TLS session on every accepted connection.

If the TLS handshake times out or raises an exception, handle_handshake_error() is called to do whatever post-mortem processing is deemed necessary.

Supports only the standard_compatible extra attribute.

Parameters
async aclose()

Close the resource.

Return type

None

property extra_attributes: Mapping[Any, Callable[Any]]

A mapping of the extra attributes to callables that return the corresponding values.

If the provider wraps another provider, the attributes from that wrapper should also be included in the returned mapping (but the wrapper may override the callables from the wrapped instance).

Return type

Mapping[Any, Callable[[], Any]]

async serve(handler, task_group=None)

Accept incoming connections as they come in and start tasks to handle them.

Parameters
  • handler (Callable[[TLSStream], Any]) – a callable that will be used to handle each accepted connection

  • task_group (Optional[TaskGroup]) – the task group that will be used to start tasks for handling each accepted connection (if omitted, an ad-hoc task group will be created)

Return type

None

Sockets and networking

async anyio.connect_tcp(remote_host, remote_port, *, local_host=None, tls=False, ssl_context=None, tls_standard_compatible=True, tls_hostname=None, happy_eyeballs_delay=0.25)

Connect to a host using the TCP protocol.

This function implements the stateless version of the Happy Eyeballs algorithm (RFC 6555). If address is a host name that resolves to multiple IP addresses, each one is tried until one connection attempt succeeds. If the first attempt does not connected within 250 milliseconds, a second attempt is started using the next address in the list, and so on. On IPv6 enabled systems, an IPv6 address (if available) is tried first.

When the connection has been established, a TLS handshake will be done if either ssl_context or tls_hostname is not None, or if tls is True.

Parameters
  • remote_host (Union[str, IPv4Address, IPv6Address]) – the IP address or host name to connect to

  • remote_port (int) – port on the target host to connect to

  • local_host (Union[str, IPv4Address, IPv6Address, None]) – the interface address or name to bind the socket to before connecting

  • tls (bool) – True to do a TLS handshake with the connected stream and return a TLSStream instead

  • ssl_context (Optional[SSLContext]) – the SSL context object to use (if omitted, a default context is created)

  • tls_standard_compatible (bool) – If True, performs the TLS shutdown handshake before closing the stream and requires that the server does this as well. Otherwise, SSLEOFError may be raised during reads from the stream. Some protocols, such as HTTP, require this option to be False. See wrap_socket() for details.

  • tls_hostname (Optional[str]) – host name to check the server certificate against (defaults to the value of remote_host)

  • happy_eyeballs_delay (float) – delay (in seconds) before starting the next connection attempt

Return type

Union[SocketStream, TLSStream]

Returns

a socket stream object if no TLS handshake was done, otherwise a TLS stream

Raises

OSError – if the connection attempt fails

async anyio.connect_unix(path)

Connect to the given UNIX socket.

Not available on Windows.

Parameters

path (Union[str, PathLike]) – path to the socket

Return type

UNIXSocketStream

Returns

a socket stream object

async anyio.create_tcp_listener(*, local_host=None, local_port=0, family=AddressFamily.AF_UNSPEC, backlog=65536, reuse_port=False)

Create a TCP socket listener.

Parameters
  • local_port (int) – port number to listen on

  • local_host (Union[str, IPv4Address, IPv6Address, None]) – IP address of the interface to listen on. If omitted, listen on all IPv4 and IPv6 interfaces. To listen on all interfaces on a specific address family, use 0.0.0.0 for IPv4 or :: for IPv6.

  • family (Literal[<AddressFamily.AF_UNSPEC: 0>, <AddressFamily.AF_INET: 2>, <AddressFamily.AF_INET6: 10>]) – address family (used if interface was omitted)

  • backlog (int) – maximum number of queued incoming connections (up to a maximum of 2**16, or 65536)

  • reuse_port (bool) – True to allow multiple sockets to bind to the same address/port (not supported on Windows)

Return type

MultiListener[SocketStream]

Returns

a list of listener objects

async anyio.create_unix_listener(path, *, mode=None, backlog=65536)

Create a UNIX socket listener.

Not available on Windows.

Parameters
  • path (Union[str, PathLike]) – path of the socket

  • mode (Optional[int]) – permissions to set on the socket

  • backlog (int) – maximum number of queued incoming connections (up to a maximum of 2**16, or 65536)

Return type

SocketListener

Returns

a listener object

Changed in version 3.0: If a socket already exists on the file system in the given path, it will be removed first.

async anyio.create_udp_socket(family=AddressFamily.AF_UNSPEC, *, local_host=None, local_port=0, reuse_port=False)

Create a UDP socket.

If port has been given, the socket will be bound to this port on the local machine, making this socket suitable for providing UDP based services.

Parameters
  • family (Literal[<AddressFamily.AF_UNSPEC: 0>, <AddressFamily.AF_INET: 2>, <AddressFamily.AF_INET6: 10>]) – address family (AF_INET or AF_INET6) – automatically determined from local_host if omitted

  • local_host (Union[str, IPv4Address, IPv6Address, None]) – IP address or host name of the local interface to bind to

  • local_port (int) – local port to bind to

  • reuse_port (bool) – True to allow multiple sockets to bind to the same address/port (not supported on Windows)

Return type

UDPSocket

Returns

a UDP socket

async anyio.create_connected_udp_socket(remote_host, remote_port, *, family=AddressFamily.AF_UNSPEC, local_host=None, local_port=0, reuse_port=False)

Create a connected UDP socket.

Connected UDP sockets can only communicate with the specified remote host/port, and any packets sent from other sources are dropped.

Parameters
  • remote_host (Union[str, IPv4Address, IPv6Address]) – remote host to set as the default target

  • remote_port (int) – port on the remote host to set as the default target

  • family (Literal[<AddressFamily.AF_UNSPEC: 0>, <AddressFamily.AF_INET: 2>, <AddressFamily.AF_INET6: 10>]) – address family (AF_INET or AF_INET6) – automatically determined from local_host or remote_host if omitted

  • local_host (Union[str, IPv4Address, IPv6Address, None]) – IP address or host name of the local interface to bind to

  • local_port (int) – local port to bind to

  • reuse_port (bool) – True to allow multiple sockets to bind to the same address/port (not supported on Windows)

Return type

ConnectedUDPSocket

Returns

a connected UDP socket

async anyio.getaddrinfo(host, port, *, family=0, type=0, proto=0, flags=0)

Look up a numeric IP address given a host name.

Internationalized domain names are translated according to the (non-transitional) IDNA 2008 standard.

Note

4-tuple IPv6 socket addresses are automatically converted to 2-tuples of (host, port), unlike what socket.getaddrinfo() does.

Parameters
  • host (Union[bytearray, bytes, str]) – host name

  • port (Union[str, int, None]) – port number

  • family (int) – socket family (‘AF_INET`, …)

  • type (int) – socket type (SOCK_STREAM, …)

  • proto (int) – protocol number

  • flags (int) – flags to pass to upstream getaddrinfo()

Return type

List[Tuple[AddressFamily, SocketKind, int, str, Tuple[str, int]]]

Returns

list of tuples containing (family, type, proto, canonname, sockaddr)

anyio.getnameinfo(sockaddr, flags=0)

Look up the host name of an IP address.

Parameters
  • sockaddr (Tuple[str, int]) – socket address (e.g. (ipaddress, port) for IPv4)

  • flags (int) – flags to pass to upstream getnameinfo()

Return type

Awaitable[Tuple[str, str]]

Returns

a tuple of (host name, service name)

anyio.wait_socket_readable(sock)

Wait until the given socket has data to be read.

This does NOT work on Windows when using the asyncio backend with a proactor event loop (default on py3.8+).

Warning

Only use this on raw sockets that have not been wrapped by any higher level constructs like socket streams!

Parameters

sock (socket) – a socket object

Raises
  • ClosedResourceError – if the socket was closed while waiting for the socket to become readable

  • BusyResourceError – if another task is already waiting for the socket to become readable

Return type

Awaitable[None]

anyio.wait_socket_writable(sock)

Wait until the given socket can be written to.

This does NOT work on Windows when using the asyncio backend with a proactor event loop (default on py3.8+).

Warning

Only use this on raw sockets that have not been wrapped by any higher level constructs like socket streams!

Parameters

sock (socket) – a socket object

Raises
  • ClosedResourceError – if the socket was closed while waiting for the socket to become writable

  • BusyResourceError – if another task is already waiting for the socket to become writable

Return type

Awaitable[None]

class anyio.abc.SocketAttribute

Bases: anyio.TypedAttributeSet

class anyio.abc.SocketStream

Bases: anyio.abc.ByteStream, anyio.abc._sockets._SocketProvider

Transports bytes over a socket.

Supports all relevant extra attributes from SocketAttribute.

class anyio.abc.SocketListener

Bases: anyio.abc._streams.Listener[anyio.abc.SocketStream], anyio.abc._sockets._SocketProvider

Listens to incoming socket connections.

Supports all relevant extra attributes from SocketAttribute.

abstract async accept()

Accept an incoming connection.

Return type

SocketStream

async serve(handler, task_group=None)

Accept incoming connections as they come in and start tasks to handle them.

Parameters
  • handler (Callable[[~T_Stream], Any]) – a callable that will be used to handle each accepted connection

  • task_group (Optional[TaskGroup]) – the task group that will be used to start tasks for handling each accepted connection (if omitted, an ad-hoc task group will be created)

Return type

None

class anyio.abc.UDPSocket

Bases: anyio.abc._streams.UnreliableObjectStream[Tuple[bytes, Tuple[str, int]]], anyio.abc._sockets._SocketProvider

Represents an unconnected UDP socket.

Supports all relevant extra attributes from SocketAttribute.

async sendto(data, host, port)

Alias for send() ((data, (host, port))).

Return type

None

class anyio.abc.ConnectedUDPSocket

Bases: anyio.abc._streams.UnreliableObjectStream[bytes], anyio.abc._sockets._SocketProvider

Represents an connected UDP socket.

Supports all relevant extra attributes from SocketAttribute.

Subprocesses

async anyio.run_process(command, *, input=None, stdout=- 1, stderr=- 1, check=True, cwd=None, env=None)

Run an external command in a subprocess and wait until it completes.

See also

subprocess.run()

Parameters
Return type

CompletedProcess

Returns

an object representing the completed process

Raises

CalledProcessError – if check is True and the process exits with a nonzero return code

async anyio.open_process(command, *, stdin=- 1, stdout=- 1, stderr=- 1, cwd=None, env=None)

Start an external command in a subprocess.

See also

subprocess.Popen

Parameters
Return type

Process

Returns

an asynchronous process object

class anyio.abc.Process

Bases: anyio.abc.AsyncResource

An asynchronous version of subprocess.Popen.

abstract kill()

Kills the process.

On Windows, this calls TerminateProcess(). On POSIX systems, this sends SIGKILL to the process.

Return type

None

abstract property pid: int

The process ID of the process.

Return type

int

abstract property returncode: Optional[int]

The return code of the process. If the process has not yet terminated, this will be None.

Return type

Optional[int]

abstract send_signal(signal)

Send a signal to the subprocess.

Parameters

signal (int) – the signal number (e.g. signal.SIGHUP)

Return type

None

abstract property stderr: Optional[anyio.abc.ByteReceiveStream]

The stream for the standard error output of the process.

Return type

Optional[ByteReceiveStream]

abstract property stdin: Optional[anyio.abc.ByteSendStream]

The stream for the standard input of the process.

Return type

Optional[ByteSendStream]

abstract property stdout: Optional[anyio.abc.ByteReceiveStream]

The stream for the standard output of the process.

Return type

Optional[ByteReceiveStream]

abstract terminate()

Terminates the process, gracefully if possible.

On Windows, this calls TerminateProcess(). On POSIX systems, this sends SIGTERM to the process.

Return type

None

abstract async wait()

Wait until the process exits.

Return type

int

Returns

the exit code of the process

Synchronization

class anyio.Event

Bases: object

is_set()

Return True if the flag is set, False if not.

Return type

bool

set()

Set the flag, notifying all listeners.

Return type

DeprecatedAwaitable

statistics()

Return statistics about the current state of this event.

Return type

EventStatistics

async wait()

Wait until the flag has been set.

If the flag has already been set when this method is called, it returns immediately.

Return type

None

class anyio.Lock

Bases: object

async acquire()

Acquire the lock.

Return type

None

acquire_nowait()

Acquire the lock, without blocking.

Raises

~WouldBlock – if the operation would block

Return type

None

locked()

Return True if the lock is currently held.

Return type

bool

release()

Release the lock.

Return type

DeprecatedAwaitable

statistics()

Return statistics about the current state of this lock.

New in version 3.0.

Return type

LockStatistics

class anyio.Condition(lock=None)

Bases: object

async acquire()

Acquire the underlying lock.

Return type

None

acquire_nowait()

Acquire the underlying lock, without blocking.

Raises

~WouldBlock – if the operation would block

Return type

None

locked()

Return True if the lock is set.

Return type

bool

notify(n=1)

Notify exactly n listeners.

Return type

None

notify_all()

Notify all the listeners.

Return type

None

release()

Release the underlying lock.

Return type

DeprecatedAwaitable

statistics()

Return statistics about the current state of this condition.

New in version 3.0.

Return type

ConditionStatistics

async wait()

Wait for a notification.

Return type

None

class anyio.Semaphore(initial_value, *, max_value=None)

Bases: object

async acquire()

Decrement the semaphore value, blocking if necessary.

Return type

None

acquire_nowait()

Acquire the underlying lock, without blocking.

Raises

~WouldBlock – if the operation would block

Return type

None

property max_value: Optional[int]

The maximum value of the semaphore.

Return type

Optional[int]

release()

Increment the semaphore value.

Return type

DeprecatedAwaitable

statistics()

Return statistics about the current state of this semaphore.

New in version 3.0.

Return type

SemaphoreStatistics

property value: int

The current value of the semaphore.

Return type

int

class anyio.CapacityLimiter(total_tokens: float)

Bases: object

async acquire()

Acquire a token for the current task, waiting if necessary for one to become available.

Return type

None

acquire_nowait()

Acquire a token for the current task without waiting for one to become available.

Raises

WouldBlock – if there are no tokens available for borrowing

Return type

DeprecatedAwaitable

async acquire_on_behalf_of(borrower)

Acquire a token, waiting if necessary for one to become available.

Parameters

borrower (object) – the entity borrowing a token

Return type

None

acquire_on_behalf_of_nowait(borrower)

Acquire a token without waiting for one to become available.

Parameters

borrower (object) – the entity borrowing a token

Raises

WouldBlock – if there are no tokens available for borrowing

Return type

DeprecatedAwaitable

property available_tokens: float

The number of tokens currently available to be borrowed

Return type

float

property borrowed_tokens: int

The number of tokens that have currently been borrowed.

Return type

int

release()

Release the token held by the current task. :raises RuntimeError: if the current task has not borrowed a token from this limiter.

Return type

None

release_on_behalf_of(borrower)

Release the token held by the given borrower.

Raises

RuntimeError – if the borrower has not borrowed a token from this limiter.

Return type

None

statistics()

Return statistics about the current state of this limiter.

New in version 3.0.

Return type

CapacityLimiterStatistics

property total_tokens: float

The total number of tokens available for borrowing.

This is a read-write property. If the total number of tokens is increased, the proportionate number of tasks waiting on this limiter will be granted their tokens.

Changed in version 3.0: The property is now writable.

Return type

float

class anyio.LockStatistics(locked, owner, tasks_waiting)

Bases: object

Variables
  • locked (bool) – flag indicating if this lock is locked or not

  • owner (TaskInfo) – task currently holding the lock (or None if the lock is not held by any task)

  • tasks_waiting (int) – number of tasks waiting on acquire()

class anyio.EventStatistics(tasks_waiting)

Bases: object

Variables

tasks_waiting (int) – number of tasks waiting on wait()

class anyio.ConditionStatistics(tasks_waiting, lock_statistics)

Bases: object

Variables
class anyio.CapacityLimiterStatistics(borrowed_tokens, total_tokens, borrowers, tasks_waiting)

Bases: object

Variables
  • borrowed_tokens (int) – number of tokens currently borrowed by tasks

  • total_tokens (float) – total number of available tokens

  • borrowers (tuple) – tasks or other objects currently holding tokens borrowed from this limiter

  • tasks_waiting (int) – number of tasks waiting on acquire() or acquire_on_behalf_of()

anyio.create_event()

Create an asynchronous event object.

Return type

Event

Returns

an event object

Deprecated since version 3.0: Use Event directly.

anyio.create_lock()

Create an asynchronous lock.

Return type

Lock

Returns

a lock object

Deprecated since version 3.0: Use Lock directly.

anyio.create_condition(lock=None)

Create an asynchronous condition.

Parameters

lock (Optional[Lock]) – the lock to base the condition object on

Return type

Condition

Returns

a condition object

Deprecated since version 3.0: Use Condition directly.

anyio.create_semaphore(value, *, max_value=None)

Create an asynchronous semaphore.

Parameters
  • value (int) – the semaphore’s initial value

  • max_value (Optional[int]) – if set, makes this a “bounded” semaphore that raises ValueError if the semaphore’s value would exceed this number

Return type

Semaphore

Returns

a semaphore object

Deprecated since version 3.0: Use Semaphore directly.

anyio.create_capacity_limiter(total_tokens)

Create a capacity limiter.

Parameters

total_tokens (float) – the total number of tokens available for borrowing (can be an integer or math.inf)

Return type

CapacityLimiter

Returns

a capacity limiter object

Deprecated since version 3.0: Use CapacityLimiter directly.

Operating system signals

anyio.open_signal_receiver(*signals)

Start receiving operating system signals.

Parameters

signals (int) – signals to receive (e.g. signal.SIGINT)

Return type

DeprecatedAsyncContextManager[AsyncIterator[int]]

Returns

an asynchronous context manager for an asynchronous iterator which yields signal numbers

Warning

Windows does not support signals natively so it is best to avoid relying on this in cross-platform applications.

Warning

On asyncio, this permanently replaces any previous signal handler for the given signals, as set via add_signal_handler().

Low level operations

async anyio.lowlevel.checkpoint()

Check for cancellation and allow the scheduler to switch to another task.

Equivalent to (but more efficient than):

await checkpoint_if_cancelled()
await cancel_shielded_checkpoint()

New in version 3.0.

Return type

None

async anyio.lowlevel.checkpoint_if_cancelled()

Enter a checkpoint if the enclosing cancel scope has been cancelled.

This does not allow the scheduler to switch to a different task.

New in version 3.0.

Return type

None

async anyio.lowlevel.cancel_shielded_checkpoint()

Allow the scheduler to switch to another task but without checking for cancellation.

Equivalent to (but potentially more efficient than):

with CancelScope(shield=True):
    await checkpoint()

New in version 3.0.

Return type

None

class anyio.lowlevel.RunVar(name, default=_NoValueSet.NO_VALUE_SET)

Bases: Generic[T]

Like a ContextVar, expect scoped to the running event loop.

Compatibility

async anyio.maybe_async(__obj)

Await on the given object if necessary.

This function is intended to bridge the gap between AnyIO 2.x and 3.x where some functions and methods were converted from coroutine functions into regular functions.

Do not try to use this for any other purpose!

Return type

object

Returns

the result of awaiting on the object if coroutine, or the object itself otherwise

New in version 2.2.

anyio.maybe_async_cm(cm)

Wrap a regular context manager as an async one if necessary.

This function is intended to bridge the gap between AnyIO 2.x and 3.x where some functions and methods were changed to return regular context managers instead of async ones.

Parameters

cm (Union[ContextManager[~T], AsyncContextManager[~T]]) – a regular or async context manager

Return type

AsyncContextManager[~T]

Returns

an async context manager

New in version 2.2.

Testing and debugging

class anyio.TaskInfo(id, parent_id, name, coro)

Bases: object

Represents an asynchronous task.

Variables
  • id (int) – the unique identifier of the task

  • parent_id (Optional[int]) – the identifier of the parent task, if any

  • name (str) – the description of the task (if any)

  • coro (Coroutine) – the coroutine object of the task

anyio.get_current_task()

Return the current task.

Return type

TaskInfo

Returns

a representation of the current task

anyio.get_running_tasks()

Return a list of running tasks in the current event loop.

Return type

DeprecatedAwaitableList[TaskInfo]

Returns

a list of task info objects

async anyio.wait_all_tasks_blocked()

Wait until all other tasks are waiting for something.

Return type

None

Exceptions

exception anyio.BrokenResourceError

Bases: Exception

Raised when trying to use a resource that has been rendered unusuable due to external causes (e.g. a send stream whose peer has disconnected).

exception anyio.BusyResourceError(action)

Bases: Exception

Raised when two tasks are trying to read from or write to the same resource concurrently.

exception anyio.ClosedResourceError

Bases: Exception

Raised when trying to use a resource that has been closed.

exception anyio.DelimiterNotFound(max_bytes)

Bases: Exception

Raised during receive_until() if the maximum number of bytes has been read without the delimiter being found.

exception anyio.EndOfStream

Bases: Exception

Raised when trying to read from a stream that has been closed from the other end.

exception anyio.ExceptionGroup

Bases: BaseException

Raised when multiple exceptions have been raised in a task group.

Variables

exceptions (Sequence[BaseException]) – the sequence of exceptions raised together

exception anyio.IncompleteRead

Bases: Exception

Raised during receive_exactly() or receive_until() if the connection is closed before the requested amount of bytes has been read.

exception anyio.TypedAttributeLookupError

Bases: LookupError

Raised by extra() when the given typed attribute is not found and no default value has been given.

exception anyio.WouldBlock

Bases: Exception

Raised by X_nowait functions if X() would block.