fast-async

Fast Async

A thread based, asynchronous programming framework built for Python. Designed and optimized for speed.

Asyncio, the go-to asynchronous programming framework for Python, uses a single-threaded event loop to achieve concurrency. Although this prevents unnecessary computational overheads and race conditions, it is inherently not as fast as threads (even with inefficiencies brought along with GIL). In some scenarios where speed is of utmost importance and where computational resources are abundant, then it makes sense to use a multi-threading approach to concurrency.

Fast Async is a high-level API for Python threads, providing users with the ability to await asynchronous code, and other features such as event-driven, pubsub model (similar to Javascript's Promise.then()). It aims to serve as an alternative to asyncio, for users who require faster execution speed.

Installation

Run pip install fast-async

Running locally

Clone the repository and make the working directory src/.

Alternatively, extract the folder src/fast_async.

Benchmarks

Scenario (sample.py)

A long-running network request and an expensive operation is executed asynchronously

Result

fast-async is, on average, almost 50% faster than asyncio due to asyncio executing the two tasks almost sequentially whilst fast-async leverages threads to execute them in parallel.

FAQ

When to use fast-async

Fast-async should be used when execution speed is a higher priority. For example, uploading each frame of a video stream to a remote server. For cases where execution speed is not important, or when well-written code make the speed differences negligible, asyncio is preferred.

What about ThreadPoolExecutor?

ThreadPoolExecutor is a Python built-in class that offers some of the same functionalities as fast-async, namely the ability to wait for tasks, and limiting threads to conserve resources. However, fast-async is more feature-rich, such as the event-driven model (subscribers and callbacks) and various utility functions that mirror certain useful functionalities from other languages (such as JavaScript). Fast-async is designed to enhance developer experience when working with threads, by offering an easy-to-use interface and minimal pre-requisite knowledge.

Documentation

Decorators

@make_async

Make a function asynchronous. Functions that are decorated with make_async will return an object of type AsyncTask

Aside from its type, decorated functions can be treated as a normal function. This means arguments can be passed in, much like a regular function.

Exceptions raised within the decorated function will be caught and re-thrown in the caller thread.

Example:

from fast_async import make_async

@make_async
def hello(message):
    print("hello world")
    return message

# Awaits hello to finish executing
return_val = hello("hello world").wait()

# Prints "hello world"
print(return_val)

Classes

Package: fast_async.types.tasks

class AsyncTask(func: Callable, *args, **kwargs)

Attributes

• func: A function or Callable.
• *args: Non-keyworded arguments for func
• **kwargs: Keyworded arguments for func
• status: Current status of func (pending, success, failure)
• result: Return value of func
• thread: Thread that func is being ran on
• exception: First caught Exception raised in func

Methods

run()

Runs func on a child thread, returns None.

wait()

Awaits func to finish executing (blocks the caller thread), returns the return value of func.

subscribe(on_success: Callable, on_failure: Callable, blocks: bool = False)

Subscribes success and failure callbacks that is invoked when task is finished executing or raised an exception. Optional blocks argument controls whether subscribe blocks the caller thread (by default subscribe does not block)

Functions

set_max_threads(num: int): None

Set the max number of threads available to be consumed by tasks. Default is 64 threads. Useful when wanting to dynamically scale usage.

Example:

from fast_async import set_max_threads

set_max_threads(3) # Only allows a maximum of 3 concurrent threads

await_all(tasks: List[AsyncTask]): List

Waits for all tasks in the tasks list to finish executing, or when a task fails, then the function will immediately raise an exception and exit.

Returns a list of results corresponding to the list of tasks provided.

Similar to JavaScript's Promise.all()

Example:

from fast_async import make_async
from fast_async.utils import await_all

@make_async
def func1():
    return 1

@make_async
def func2():
    return 2

await_all([func1(), func2()]) # Will return [1, 2]

await_first(tasks: List[AsyncTask]): Any

Waits for the first task in tasks list to finish executing and immediately returns the result. If all tasks fail, then the first failed task is raised in an exception.

Returns the result of the first successful task.

Similar to JavaScript's Promise.race()

Example

from fast_async import make_async
from fast_async.utils import await_first
import time

@make_async
def func1():
    time.sleep(1)
    return 1

@make_async
def func2():
    time.sleep(2)
    return 2

await_first([func1(), func2()]) # Will return 1, because func1 finishes first