# TODO: import from typing when deprecating Python 3.9
from typing_extensions import Annotated, Doc


class OAuth2PasswordRequestForm:
    """
    This is a dependency class to collect the `username` and `password` as form data
    for an OAuth2 password flow.

    The OAuth2 specification dictates that for a password flow the data should be
    collected using form data (instead of JSON) and that it should have the specific

from typing import Annotated

from fastapi import FastAPI, Path
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(
    item_id: Annotated[int, Path(title="The ID of the item to get", ge=0, le=1000)],
    q: str | None = None,
    item: Item | None = None,

এই টাইপগুলি এবং অভ্যন্তরীণ টাইপগুলি ঘোষণা করতে, আপনি Python মডিউল `typing` ব্যবহার করতে পারেন। এটি বিশেষভাবে এই টাইপ হিন্টগুলি সমর্থন করার জন্য রয়েছে।

#### Python এর নতুন সংস্করণ

`typing` ব্যবহার করা সিনট্যাক্সটি Python 3.6 থেকে সর্বশেষ সংস্করণগুলি পর্যন্ত, অর্থাৎ Python 3.9, Python 3.10 ইত্যাদি সহ সকল সংস্করণের সাথে **সামঞ্জস্যপূর্ণ**।

from fastapi import FastAPI, Form
from typing_extensions import Annotated

app = FastAPI()


@app.post("/login/")
async def login(username: Annotated[str, Form()], password: Annotated[str, Form()]):

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError
from typing_extensions import Annotated

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[list[str], Query()] = ["foo", "bar"]):
    query_items = {"q": q}

    ```

## `Union` 或者 `anyOf`

响应可以声明为两种类型的 `Union` 类型，即该响应可以是两种类型中的任意类型。

在 OpenAPI 中可以使用 `anyOf` 定义。

为此，请使用 Python 标准类型提示 <a href="https://docs.python.org/3/library/typing.html#typing.Union" class="external-link" target="_blank">`typing.Union`</a>：

!!! note "笔记"

from typing import Annotated, Union

from fastapi import Depends, FastAPI

app = FastAPI()


fake_items_db = [{"item_name": "Foo"}, {"item_name": "Bar"}, {"item_name": "Baz"}]


class CommonQueryParams:
    def __init__(self, q: Union[str, None] = None, skip: int = 0, limit: int = 100):
        self.q = q
        self.skip = skip
        self.limit = limit


@app.get("/items/")

from fastapi import Depends, FastAPI, HTTPException
from typing_extensions import Annotated

app = FastAPI()


class InternalError(Exception):
    pass


def get_username():
    try:
        yield "Rick"
    except InternalError:
        print("Oops, we didn't raise again, Britney 😱")


@app.get("/items/{item_id}")
def get_item(item_id: str, username: Annotated[str, Depends(get_username)]):
    if item_id == "portal-gun":

from fastapi import Depends, FastAPI
from fastapi.security import HTTPBasic, HTTPBasicCredentials
from typing_extensions import Annotated

app = FastAPI()

security = HTTPBasic()


@app.get("/users/me")
def read_current_user(credentials: Annotated[HTTPBasicCredentials, Depends(security)]):