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How to Use Coroutine As A Pytest Fixture?

2 minutes read

Using coroutine as a pytest fixture involves creating an async function marked with the @pytest.fixture decorator. This function should yield the coroutine so that it can be awaited during tests. When using this fixture in a test, the test function should also be marked with the async keyword so that it can properly await the coroutine provided by the fixture. This allows for asynchronous operations to be set up before each test and ensures that the test code is executed in the correct order.


What is the asyncio.run() function used for in Python?

The asyncio.run() function in Python is used to run a coroutine and return the result. It is typically used as the main entry point for running asynchronous code using the asyncio module. The asyncio.run() function can only be called from the main thread, and it is recommended to be used at the top level of the script.


How to check if a function is a coroutine in Python?

In Python, you can check if a function is a coroutine by using the inspect module. Here's an example code snippet that demonstrates how to check if a function is a coroutine:

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import inspect

async def my_coroutine_function():
    return "Hello, I am a coroutine!"

def my_regular_function():
    return "Hello, I am a regular function!"

# Check if a function is a coroutine
if inspect.iscoroutinefunction(my_coroutine_function):
    print("my_coroutine_function is a coroutine")
else:
    print("my_coroutine_function is not a coroutine")

if inspect.iscoroutinefunction(my_regular_function):
    print("my_regular_function is a coroutine")
else:
    print("my_regular_function is not a coroutine")


When you run this code, it will output:

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my_coroutine_function is a coroutine
my_regular_function is not a coroutine


As you can see, the iscoroutinefunction function from the inspect module correctly identifies the coroutine function my_coroutine_function as a coroutine, and the regular function my_regular_function as not a coroutine.


How to cancel a coroutine in Python?

You can cancel a coroutine in Python by using the cancel() method provided by the asyncio.Task object. Here is an example:

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import asyncio

async def my_coroutine():
    try:
        while True:
            print('Running...')
            await asyncio.sleep(1)
    except asyncio.CancelledError:
        print('Coroutine canceled')

loop = asyncio.get_event_loop()
task = loop.create_task(my_coroutine())

# Cancel the coroutine after 5 seconds
loop.call_later(5, task.cancel)

try:
    loop.run_until_complete(task)
except asyncio.CancelledError:
    pass


In this example, we create a coroutine called my_coroutine() that runs indefinitely and prints "Running..." every second. We then create a asyncio.Task object from this coroutine and use call_later() to cancel the task after 5 seconds. When the task is canceled, it will raise an asyncio.CancelledError exception, which we catch and handle by printing "Coroutine canceled".

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