Highlights
This release adds support for dependencies and parameters using Annotated and recommends its usage. ✨
This has several benefits, one of the main ones is that now the parameters of your functions with Annotated would not be affected at all.
If you call those functions in other places in your code, the actual default values will be kept, your editor will help you notice missing required arguments, Python will require you to pass required arguments at runtime, you will be able to use the same functions for different things and with different libraries (e.g. Typer will soon support Annotated too, then you could use the same function for an API and a CLI), etc.
Because Annotated is standard Python, you still get all the benefits from editors and tools, like autocompletion, inline errors, etc.
One of the biggest benefits is that now you can create Annotated dependencies that are then shared by multiple path operation functions, this will allow you to reduce a lot of code duplication in your codebase, while keeping all the support from editors and tools.
For example, you could have code like this:
def get_current_user(token: str):
# authenticate user
return User()
@app.get("/items/")
def read_items(user: User = Depends(get_current_user)):
...
@app.post("/items/")
def create_item(*, user: User = Depends(get_current_user), item: Item):
...
@app.get("/items/{item_id}")
def read_item(*, user: User = Depends(get_current_user), item_id: int):
...
@app.delete("/items/{item_id}")
def delete_item(*, user: User = Depends(get_current_user), item_id: int):
...There's a bit of code duplication for the dependency:
user: User = Depends(get_current_user)...the bigger the codebase, the more noticeable it is.
Now you can create an annotated dependency once, like this:
CurrentUser = Annotated[User, Depends(get_current_user)]And then you can reuse this Annotated dependency:
CurrentUser = Annotated[User, Depends(get_current_user)]
@app.get("/items/")
def read_items(user: CurrentUser):
...
@app.post("/items/")
def create_item(user: CurrentUser, item: Item):
...
@app.get("/items/{item_id}")
def read_item(user: CurrentUser, item_id: int):
...
@app.delete("/items/{item_id}")
def delete_item(user: CurrentUser, item_id: int):
......and CurrentUser has all the typing information as User, so your editor will work as expected (autocompletion and everything), and FastAPI will be able to understand the dependency defined in Annotated. 😎
Roughly all the docs have been rewritten to use Annotated as the main way to declare parameters and dependencies. All the examples in the docs now include a version with Annotated and a version without it, for each of the specific Python versions (when there are small differences/improvements in more recent versions). There were around 23K new lines added between docs, examples, and tests. 🚀
The key updated docs are:
- Python Types Intro:
- Tutorial:
Special thanks to @nzig for the core implementation and to @adriangb for the inspiration and idea with Xpresso! 🚀