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✏ Fix grammar and add helpful links to dependencies in `docs/en/docs/async.md` (#5432)

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Pamela Fox 2022-10-31 10:21:05 -07:00 committed by GitHub
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@ -403,17 +403,17 @@ All that is what powers FastAPI (through Starlette) and what makes it have such
When you declare a *path operation function* with normal `def` instead of `async def`, it is run in an external threadpool that is then awaited, instead of being called directly (as it would block the server).
If you are coming from another async framework that does not work in the way described above and you are used to define trivial compute-only *path operation functions* with plain `def` for a tiny performance gain (about 100 nanoseconds), please note that in **FastAPI** the effect would be quite opposite. In these cases, it's better to use `async def` unless your *path operation functions* use code that performs blocking <abbr title="Input/Output: disk reading or writing, network communications.">I/O</abbr>.
If you are coming from another async framework that does not work in the way described above and you are used to defining trivial compute-only *path operation functions* with plain `def` for a tiny performance gain (about 100 nanoseconds), please note that in **FastAPI** the effect would be quite opposite. In these cases, it's better to use `async def` unless your *path operation functions* use code that performs blocking <abbr title="Input/Output: disk reading or writing, network communications.">I/O</abbr>.
Still, in both situations, chances are that **FastAPI** will [still be faster](/#performance){.internal-link target=_blank} than (or at least comparable to) your previous framework.
### Dependencies
The same applies for dependencies. If a dependency is a standard `def` function instead of `async def`, it is run in the external threadpool.
The same applies for [dependencies](/tutorial/dependencies/index.md){.internal-link target=_blank}. If a dependency is a standard `def` function instead of `async def`, it is run in the external threadpool.
### Sub-dependencies
You can have multiple dependencies and sub-dependencies requiring each other (as parameters of the function definitions), some of them might be created with `async def` and some with normal `def`. It would still work, and the ones created with normal `def` would be called on an external thread (from the threadpool) instead of being "awaited".
You can have multiple dependencies and [sub-dependencies](/tutorial/dependencies/sub-dependencies.md){.internal-link target=_blank} requiring each other (as parameters of the function definitions), some of them might be created with `async def` and some with normal `def`. It would still work, and the ones created with normal `def` would be called on an external thread (from the threadpool) instead of being "awaited".
### Other utility functions