ntessore/coroutines

Python coroutines without an event loop

coroutines — Python coroutines without an event loop

This is a small package which provides tools to run async functions and generators without an asyncio event loop.

The coroutines module provides functions such as coroutines.run(), coroutines.gather(), and coroutines.sleep() that work just like their asyncio counterparts, but without scheduling any tasks in an external event loop. For example, the following code was adapted from the asyncio documentation:

import coroutines

async def factorial(name, number):
    f = 1
    for i in range(2, number + 1):
        print(f"Task {name}: Compute factorial({number}), currently i={i}...")
        await coroutines.sleep()  # CHANGED: no argument
        f *= i
    print(f"Task {name}: factorial({number}) = {f}")
    return f

async def main():
    # Schedule three calls *concurrently*:
    L = await coroutines.gather(
        factorial("A", 2),
        factorial("B", 3),
        factorial("C", 4),
    )
    print(L)

coroutines.run(main())

# Expected output:
#
#     Task A: Compute factorial(2), currently i=2...
#     Task B: Compute factorial(3), currently i=2...
#     Task C: Compute factorial(4), currently i=2...
#     Task A: factorial(2) = 2
#     Task B: Compute factorial(3), currently i=3...
#     Task C: Compute factorial(4), currently i=3...
#     Task B: factorial(3) = 6
#     Task C: Compute factorial(4), currently i=4...
#     Task C: factorial(4) = 24
#     [2, 6, 24]

The example produces the same result as the asyncio code by simply calling, suspending, and resuming the coroutines until they are completed. Practically, the only difference between the coroutines and asyncio examples is that coroutines.sleep() does not take an argument. Because there is no external event loop, a call to coroutines.sleep() cannot suspend the current chain of coroutines for a fixed amount of time, but only until it is resumed at the next iteration.

Running coroutines

coroutines.run(coro) #

Run a coroutine from synchronous code.

Suspending coroutines

awaitable coroutines.sleep() #

Suspend the current chain of coroutines, allowing another coroutine to run concurrently.

Concurrent execution

awaitable coroutines.gather(*aws) #

Run the given awaitables aws concurrently.

Returns a coroutine that loops over aws, resuming each awaitable in turn until it is suspended again or finished. Execution is suspended after each pass over aws, so that other coroutines can run while the result of gather() is being awaited.

The result of awaiting gather() is the aggregate list of awaited results from aws in the same order.

Creating awaitables

The coroutines module contains a number of helper functions that turn regular objects into awaitable variants of themselves.

awaitable coroutines.awaitable(obj=None) #

Create an awaitable variant of obj. Returns a coroutine that awaits coroutines.sleep() before returning obj.

awaitable coroutines.aiterable(iterable) #

Create an awaitable variant of an iterable. Returns an asynchronous generator that awaits coroutines.sleep() before each item in iterable.

awaitable coroutines.arange(stop) #
awaitable coroutines.arange(start, stop[, step])

Create an awaitable variant of range(). Returns an asynchronous generator that awaits coroutines.sleep() before each number.