Asyncio.cancel() a cancellation utility as a coroutine

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The good at Python have come up with a solution: Asyncio.cancel() as a coroutine. Yes, you heard me right a cancellation utility that’s also a coroutine. It’s like the ultimate power-up for your async game.

But what exactly does this mean? Let’s break it down.

First off, why we need a cancellation utility in the first place. In traditional programming, you can simply call `task.cancel()` and be done with it. But in async land, things are not so simple. When you cancel a task using `asyncio.create_task(my_function())`, your program continues to run without waiting for that task to finish. This means that if the task is taking longer than expected (or worse, forever), your program will never actually complete.

To solve this problem, we need a way to wait for the cancelled task to finish before moving on. And that’s where Asyncio.cancel() as a coroutine comes in. By wrapping our cancellation code in a coroutine, we can await its completion and handle any errors or exceptions that may arise.

Here’s an example:

# Import the necessary modules
import asyncio
from time import sleep

# Define a coroutine function
async def my_function():
    print("Starting function...")
    while True:
        # Do some work here...
        await asyncio.sleep(1) # Use asyncio.sleep() to pause the execution of the coroutine for 1 second

# Define the main coroutine function
async def main():
    task = asyncio.create_task(my_function()) # Create a task for the my_function coroutine
    try:
        await asyncio.sleep(2) # Wait for 2 seconds before cancelling the task
        print("Cancelling function...")
        cancel_coro = asyncio.cancel(task) # Use asyncio.cancel() to cancel the task
        done, pending = await asyncio.wait([task, cancel_coro], return_when=asyncio.FIRST_COMPLETED) # Wait for either the task or the cancellation coroutine to complete
        for t in done:
            if t is task:
                print("Function cancelled!")
    except Exception as e:
        # Handle any errors or exceptions that may arise
        print(f"An error occurred: {e}")

# Run the main coroutine function
asyncio.run(main()) # Use asyncio.run() to run the main coroutine function

In this example, we’re creating a task using `create_task()`, and then waiting for 2 seconds before cancelling it using the new Asyncio.cancel() as a coroutine. We’re also awaiting both the original task and the cancellation coroutine to finish using `asyncio.wait()`.

The output of this program should look something like:

# Importing the necessary libraries
import asyncio

# Defining a function to create a task
async def create_task():
    print("Starting function...") # Prints a message to indicate the function has started
    await asyncio.sleep(2) # Waits for 2 seconds before continuing
    print("Function completed!") # Prints a message to indicate the function has completed

# Creating a task using the create_task() function
task = asyncio.create_task(create_task())

# Defining a coroutine to cancel the task
async def cancel_task():
    print("Cancelling function...") # Prints a message to indicate the function has started
    task.cancel() # Cancels the task created earlier
    print("Function cancelled!") # Prints a message to indicate the function has completed

# Waiting for both the original task and the cancellation coroutine to finish using asyncio.wait()
# Note: asyncio.wait() takes in a list of coroutines and returns a tuple of completed and pending tasks
# We use the * operator to unpack the tuple and pass the tasks as separate arguments to asyncio.wait()
completed_tasks, pending_tasks = await asyncio.wait(task, cancel_task())

# Printing the output
print("Here is the output:")
print(completed_tasks) # Prints the completed tasks
print(pending_tasks) # Prints the pending tasks

cancel() as a coroutine, the ultimate power-up for your async game. With great cancellation comes great responsibility (or something like that). But hey, at least now we can finally let go of those stubborn tasks and move on with our lives.

SICORPS