"Run arbitrary tasks in contexts associated with a single thread."
Python microlibrary to run arbitrary tasks in contexts associated with a single thread.
CAVEAT: This library is currently not well tested and requires unit tests for many more different scenarios. Any contribution would be greatly appreciated.
Simply install using
pip install threadswitch.
ThreadSwitch currently implements two kinds of thread contexts:
A context associated with a background thread which must be manually closed. This context is best suited for system
resources which are restricted to the same thread, such as OpenGL and SQLite3 objects (in a standard CPython installation).
While it provides
reset methods to manage thread lifetime, it is recommended to use it with a
context manager (i.e. the
from threadswitch import PersistentContext import sqlite3 def init_sqlite_ctx(ctx: PersistentContext): ctx.db = sqlite3.connect('my.db') def clean_sqlite_ctx(ctx: PersistentContext): ctx.db.close() with PersistentContext() as ctx: @ctx.task def execute(sql, params): ctx.db.execute(sql, params) # Note: As sqlite3.Cursor objects are also thread-bound, operating on one requires a more complex proxy wrapper. # This is skipped in this simple example usage. execute('DROP TABLE foobar').join()
A context which automatically terminates its background thread once it's processed its pending task queue. This is useful to simply synchronize access to a common system resource, such as the CLI. When closed, dispatching a new task will automatically restart the background thread.
The thread can be kept alive past the completion of the queue. This is useful to avoid unnecessary thread creation and termination overhead in a slowly paced environment. It is recommended to use a timeout of a fraction of a second in general.
from threadswitch import RebootContext from sys import stdout, stdin ctx = RebootContext(task_wait_time=.1) writeline = ctx.task(stdout.writeline) readline = ctx.task(stdin.readline) writeline('foobar') value = readline().result()
The above sections outline the differences between the two currently implemented context types, but they share various common behaviors.
As seen in the above examples, one may use
ctx.task to create a new dispatchable task. Internally, this simply creates
a wrapper function which calls
ctx.dispatch(*args, **kwargs) upon invocation. They can be used in two different styles:
threaded and asyncio styles.
ctx.task method can also be used as a decorator as follows:
from threadswitch import RebootContext from sys import stdin ctx = RebootContext(0.5) @ctx.task def read(n: int = -1): if n == -1: return stdin.readline() return stdin.read(n) read().result()
The examples above use "threaded usage style." This style uses
exception methods on the task
objects returned by dispatched tasks to synchronize threads.
join simply waits until the task completes either by
returning a result value, or by raising an exception.
result retrieves the return value of the task, and
retrieves any occurred exception encountered during the task if applicable. If the task is incomplete, implicitly
All of these methods support a
timeout argument which may be either
None or a number in seconds.
Alternatively, one may simply
await any dispatched task. This behaves as one would expect from any other
If the task was successful, retrieves the result value. If the task encountered an exception, raises the exception in
this thread. As this syntax does not support a timeout, one may alternatively use
await asyncio.wait_for(..., timeout=...).
Copyright (c) 2021 Kiruse
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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