Sometimes your FastAPI dependencies have to get value from functions cannot be available on initialization. The problem is particularly acute to use class dependencies with inheritance. This project try to solve problem of modify Depends
after application initialization.
pip install fastapi-depends-ext
from typing import List
from fastapi import Depends
from fastapi import FastAPI
from fastapi import Query
from pydantic import conint
from fastapi_depends_ext import DependsAttr
from fastapi_depends_ext import DependsAttrBinder
class ItemsPaginated(DependsAttrBinder):
_items = list(range(100))
async def get_page(self, page: conint(ge=1) = Query(1)):
return page
async def items(self, page: int = DependsAttr("get_page")):
_slice = slice(page * 10, (page + 1) * 10)
return self._items[_slice]
class ItemsSquarePaginated(ItemsPaginated):
async def items(self, items: List[int] = DependsAttr("items", from_super=True)):
return [i**2 for i in items]
app = FastAPI()
@app.get("/")
def items_list(items: List[int] = Depends(ItemsPaginated().items)) -> List[int]:
return items
@app.get("/square")
def items_list_square(items: List[int] = Depends(ItemsSquarePaginated().items)) -> List[int]:
return items
Use DependsAttr
to Depends
from current instance attributes. All examples use asyncio
, but you can write all methods synchronous.
DependsAttr
support next properties:
callable
object)property
(must return callable
that will be used as dependency)Your class must inherit from DependsAttrBinder
and attributes must be DependsAttr
. DependsAttrBinder
automatically patch all methods with DependsAttr
by instance attributes.
DependsAttr
arguments:
method_name
- str
, name of instance attribute to use as dependencyfrom_super
- bool
, on true, will use attribute method_name
from super class like super().method_name()
use_cache
- bool
, allow to cache depends result for the same dependencies in requestUseless(?) class created to proof of concept of patching methods and correct work FastAPI
applications.
DependsExt
allow you define default values of method arguments after FastAPI
endpoint has been created.
Example:
from fastapi import FastAPI
from fastapi import Query
from fastapi_depends_ext import DependsExt
def pagination(page: int = Query()):
return page
depends = DependsExt(pagination)
app = FastAPI()
@app.on_event("startup")
def setup_depends():
depends.bind(page=Query(1))
@app.get("/")
def get_method(value: int = depends) -> int:
return value
Is equivalent for
from fastapi import Depends
from fastapi import FastAPI
from fastapi import Query
def pagination(page: int = Query(1)):
return page
app = FastAPI()
@app.get("/")
def get_method(value: int = Depends(pagination)) -> int:
return value