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Let's write some code

Now we take the starlette example from usages and specify it to use Path now.

Handle request specific fields

First of all, Starlette pass to a handler the only one argument - request To use them with FastDepends we need unwrap request to kwargs.

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from fast_depends import inject


def wrap_starlette(func):
    async def wrapper(request):
        return await inject(func)(
            request=request
        )
    return wrapper

Also, we wraps an original handler to fast_depends.inject too at 3 line

Declare Custom Field

Next step, define Path custom field

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from fast_depends.library import CustomField


class Path(CustomField):
    def use(self, /, *, request, **kwargs):
        return {
            **super().use(request=request, **kwargs),
            self.param_name: request.path_params.get(self.param_name)
        }

Usage with the Starlette

And use it at our Starlette application: 

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from starlette.applications import Starlette
from starlette.responses import PlainTextResponse
from starlette.routing import Route


async def hello(user: str = Path()):
    return PlainTextResponse(f"Hello, {user}!")

app = Starlette(debug=True, routes=[
    Route("/{user}", hello)
])

Depends is working as expected too

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def get_user(user_id: int = Path()):
    return f"user {user_id}"

@wrap_starlette
async def hello(user: str = Depends(get_user)):
    return PlainTextResponse(f"Hello, {user}!")

app = Starlette(debug=True, routes=[
    Route("/{user_id}", hello)
])

As an Annotated does 

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@wrap_starlette
async def get_user(user: Annotated[int, Path()]):
    return PlainTextResponse(f"Hello, {user}!")

Full example

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from fast_depends import inject
from fast_depends.library import CustomField

from starlette.applications import Starlette
from starlette.responses import PlainTextResponse
from starlette.routing import Route

class Path(CustomField):
    def use(self, /, *, request, **kwargs):
        return {
            **super().use(request=request, **kwargs),
            self.param_name: request.path_params.get(self.param_name)
        }

def wrap_starlette(func):
    async def wrapper(request):
        return await inject(func)(
            request=request
        )
    return wrapper

@wrap_starlette
async def hello(user: str = Path()):
    return PlainTextResponse(f"Hello, {user}!")

app = Starlette(debug=True, routes=[
    Route("/{user}", hello)
])

The code above works "as it". You can copy it and declare other Header, Cookie, Query fields by yourself. Just try, it's fun!