We Are Going To Discuss About Python 3.10 asyncio.gather() shows DeprecationWarning: There is no current event loop. So lets Start this Python Article.
Python 3.10 asyncio.gather() shows DeprecationWarning: There is no current event loop
- How to solve Python 3.10 asyncio.gather() shows DeprecationWarning: There is no current event loop
According to the documentation, this happens because there is no event loop running at the time when you call
gather.
Deprecated since version 3.10: Deprecation warning is emitted if no positional arguments are provided or not all positional arguments are Future-like objects and there is no running event loop.
As you've probably noticed, your code works. It will continue to work and you can ignore the deprecation warning as long as you use 3.10. At some point in the future, though, this may change to a runtime error.
If you'll bear with me a moment, the recommended way to run an event loop is withrun, notloop.run_until_complete.def aggregate_results(projects: list): results = asyncio.run(asyncio.gather(*(do_request(project) for project in projects))) return zip(projects, results)
This, however, won't actually work. You'll instead get an exceptionValueError: a coroutine was expected, got <_GatheringFuture pending>
The fix is to instead awaitgatherfrom another coroutine.async def get_project_results(projects: list): results = await asyncio.gather(*(do_request(project) for project in projects)) return results def aggregate_results(projects: list): results = asyncio.run(get_project_results(projects)) return zip(projects, results)
(You could also useget_project_resultswith your version ofaggregate_results.) - Python 3.10 asyncio.gather() shows DeprecationWarning: There is no current event loop
According to the documentation, this happens because there is no event loop running at the time when you call
gather.
Deprecated since version 3.10: Deprecation warning is emitted if no positional arguments are provided or not all positional arguments are Future-like objects and there is no running event loop.
As you've probably noticed, your code works. It will continue to work and you can ignore the deprecation warning as long as you use 3.10. At some point in the future, though, this may change to a runtime error.
If you'll bear with me a moment, the recommended way to run an event loop is withrun, notloop.run_until_complete.def aggregate_results(projects: list): results = asyncio.run(asyncio.gather(*(do_request(project) for project in projects))) return zip(projects, results)
This, however, won't actually work. You'll instead get an exceptionValueError: a coroutine was expected, got <_GatheringFuture pending>
The fix is to instead awaitgatherfrom another coroutine.async def get_project_results(projects: list): results = await asyncio.gather(*(do_request(project) for project in projects)) return results def aggregate_results(projects: list): results = asyncio.run(get_project_results(projects)) return zip(projects, results)
(You could also useget_project_resultswith your version ofaggregate_results.)
Solution 1
According to the documentation, this happens because there is no event loop running at the time when you call gather.
Deprecated since version 3.10: Deprecation warning is emitted if no positional arguments are provided or not all positional arguments are Future-like objects and there is no running event loop.
As you’ve probably noticed, your code works. It will continue to work and you can ignore the deprecation warning as long as you use 3.10. At some point in the future, though, this may change to a runtime error.
If you’ll bear with me a moment, the recommended way to run an event loop is with run, not loop.run_until_complete.
def aggregate_results(projects: list):
results = asyncio.run(asyncio.gather(*(do_request(project) for project in projects)))
return zip(projects, results)
This, however, won’t actually work. You’ll instead get an exception
ValueError: a coroutine was expected, got <_GatheringFuture pending>
The fix is to instead await gather from another coroutine.
async def get_project_results(projects: list):
results = await asyncio.gather(*(do_request(project) for project in projects))
return results
def aggregate_results(projects: list):
results = asyncio.run(get_project_results(projects))
return zip(projects, results)
(You could also use get_project_results with your version of aggregate_results.)
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Conclusion
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