pymap.concurrent

Implements some concurrency utilities used by pymap. Each has an implementation using asyncio and threading concurrency primitives.

class pymap.concurrent.Subsystem

Utility for creating concurrency primitives for a subsystem, either asyncio or threading.

classmethod for_executor(executor)

Return a subsystem based on the given executor. If executor is None, use asyncio. If executor is a concurrent.futures.ThreadPoolExecutor, use threading.

Parameters:

executor (Executor | None) – The executor in use, if any.

Return type:

Subsystem

classmethod for_asyncio()

Return a subsystem for asyncio.

Return type:

Subsystem

classmethod for_threading(executor)

Return a subsystem for threading.

Parameters:

executor (ThreadPoolExecutor)

Return type:

Subsystem

abstract property subsystem: str

The subsystem name, 'asyncio' or 'threading'.

abstract execute(future)

Executes the future and returns its result in the subsystem. For asyncio, this simply means return await future. For threading, it uses run_in_executor() to run the future in another thread.

Parameters:

future (Awaitable[RetT]) – An awaitable result to execute by the subsystem.

Return type:

Awaitable[RetT]

abstract new_rwlock()

Return a new read-write lock.

Return type:

ReadWriteLock

abstract new_event()

Return a new concurrent event.

Return type:

Event

class pymap.concurrent.Event

Concurrent event, one thread signals and any waiting event is released.

classmethod for_asyncio()

Return an event for asyncio.

Return type:

Event

classmethod for_threading()

Return an event for threading.

Return type:

Event

abstract property subsystem: str

The subsystem the event was created for, 'asyncio' or 'threading'.

abstract or_event(*events)

Return a new event that is signalled when either the current event or any of the provided events are signalled.

Parameters:

• self (EventT)

• events (EventT)

Return type:

EventT

abstract is_set()

Return True if the event is set.

Return type:

bool

abstract set()

Signal the waiting threads to release.

Return type:

None

abstract clear()

Clear the signal, allowing threads to wait again.

Return type:

None

abstract async wait(*, timeout=None)

Wait until another thread signals the event.

Parameters:

timeout (float | None) – Maximum time to wait, in seconds.

Return type:

None

class pymap.concurrent.ReadWriteLock

Read-write lock.

classmethod for_asyncio()

Return a read-write lock for asyncio.

Return type:

ReadWriteLock

classmethod for_threading()

Return a read-write lock for threading.

Return type:

ReadWriteLock

abstract property subsystem: str

The subsystem the read-write lock was created for, 'asyncio' or 'threading'.

abstract read_lock()

Acquires a read-lock, blocking until any write-locks are released.

Return type:

AbstractAsyncContextManager[None]

abstract write_lock()

Acquires a write-lock, blocking until all read- or write-locks are released.

Return type:

AbstractAsyncContextManager[None]

class pymap.concurrent.FileLock(path, expiration=600.0, read_retry_delay=(0.01, 0.03, 0.06, 0.1, 0.15, 0.25, 0.4, 0.5, 0.5, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0), write_retry_delay=(0.01, 0.03, 0.06, 0.1, 0.15, 0.25, 0.4, 0.5, 0.5, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0))

Uses the presence or absence of a file on the filesystem to simulate a read-write lock. If the file is present, other read- and write-locks will block until the file is gone. If the file is absent, read-locks will not block. Write-locks will create the file on acquire and remove it on release.

The delay arguments are a sequence of floats used as the duration of successive sleep() calls. If this sequence is exhausted before a lock is established, TimeoutError is thrown.

Parameters:

• path (str) – The path of the lock file.

• expiration (float) – Lock files older than this age will be deleted.

• read_retry_delay (_Delay) – The delay sequence between read-lock attempts.

• write_retry_delay (_Delay) – The delay sequence between write-lock attempts.

property subsystem: str

The subsystem the read-write lock was created for, 'file'.

read_lock()

Acquires a read-lock, blocking until any write-locks are released.

Return type:

AsyncIterator[None]

write_lock()

Acquires a write-lock, blocking until all read- or write-locks are released.

Return type:

AsyncIterator[None]

class pymap.concurrent.EventT

Type variable with an upper bound of Event.

alias of TypeVar(‘EventT’, bound=Event)

class pymap.concurrent.RetT

Type variable for any return type.

alias of TypeVar(‘RetT’)