Enable tracemalloc to get the object allocation traceback

# Enable tracemalloc to get the object allocation traceback

The Python "RuntimeWarning: Enable tracemalloc to get the object allocation traceback" occurs when you forget to await a coroutine.

To resolve the issue, make sure to await all coroutines in your Python script.

Here is an example of when the warning is shown.

main.py

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import asyncio


async def my_coroutine():
    print('bobby')

    # ⛔️ RuntimeWarning: coroutine 'sleep' was never awaited
    #   asyncio.sleep(0.5)
    # RuntimeWarning: Enable tracemalloc to get the object allocation traceback

    asyncio.sleep(0.5) # 👈️ Forgot to await asyncio.sleep()

    print('hadz.com')


loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)


async def main():
    tasks = []
    asyncio.create_task(my_coroutine())

    tasks.append(asyncio.create_task(my_coroutine()))

    await asyncio.wait(tasks)

loop.run_until_complete(main())
loop.close()

runtime warning enable tracemalloc to get the object allocation traceback

The issue occurred because I forgot to await the coroutine that is returned from asyncio.sleep().

# Make sure to `await` all coroutines to resolve the issue

I just have to add the await keyword to await the coroutine to resolve the issue.

In other words, this:

main.py

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# ⛔️ Incorrect
asyncio.sleep(0.5)

Becomes this:

main.py

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# ✅ Correct
await asyncio.sleep(0.5)

Here is the complete example.

main.py

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import asyncio


async def my_coroutine():
    print('bobby')

    asyncio.sleep(0.5)

    print('hadz.com')


loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)


async def main():
    tasks = []
    asyncio.create_task(my_coroutine())

    tasks.append(asyncio.create_task(my_coroutine()))

    await asyncio.wait(tasks)

loop.run_until_complete(main())
loop.close()

await all coroutines

The code for this article is available on GitHub

You have to await all coroutines in your code.

For example, coroutines are returned from calls to asyncio.sleep() and asyncio.wait().

You can hover over a method in your IDE to see if it returns a coroutine.

Here is an example that does that in VS Code.

check if method returns coroutine

# You also need to await `async` functions

Note that async functions are also awaitable.

For example, the following code sample shows the warning.

main.py

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import asyncio


async def greet(name):
    return f'hello {name}'


async def main():
    # ⛔️ RuntimeWarning: Enable tracemalloc to get the object allocation traceback
    greet('bobby hadz') # 👈️ Forgot to await greet()

asyncio.run(main())

forgetting to await async functions

The warning is shown because I forgot to await the greet async function.

Here is the corrected version of the code.

main.py

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import asyncio


async def greet(name):
    return f'hello {name}'


async def main():
    print(await greet('bobby hadz'))

asyncio.run(main())

make sure to await async functions

The code for this article is available on GitHub

Python coroutines are awaitable so they can be awaited from other coroutines.

A coroutine is considered to be:

a coroutine function: an async def function.
a coroutine object: an object that is returned by calling a coroutine function.

If you need to call an async function outside an event loop, use the asyncio.run() method.

main.py

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import asyncio


async def greet(name):
    return f'hello {name}'


print(asyncio.run(greet('bobby hadz')))

using asyncio run method

The code for this article is available on GitHub

# Additional Resources

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Enable tracemalloc to get the object allocation traceback