# Reference

Here's the reference or code API, the classes, functions, parameters, attributes, and
all the FastAPI parts you can use in your applications.

If you want to **learn FastAPI** you are much better off reading the

from typing import Union

from fastapi import FastAPI
from fastapi.responses import FileResponse
from pydantic import BaseModel


class Item(BaseModel):
    id: str
    value: str


responses = {
    404: {"description": "Item not found"},
    302: {"description": "The item was moved"},
    403: {"description": "Not enough privileges"},
}


app = FastAPI()


@app.get(
    "/items/{item_id}",

from typing import Union

from fastapi import Body, FastAPI, status
from fastapi.responses import JSONResponse

app = FastAPI()

items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "size": 3}}


@app.put("/items/{item_id}")
async def upsert_item(
    item_id: str,
    name: Union[str, None] = Body(default=None),
    size: Union[int, None] = Body(default=None),
):
    if item_id in items:

from typing import Annotated

from fastapi import Body, FastAPI, status
from fastapi.responses import JSONResponse

app = FastAPI()

items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "size": 3}}


@app.put("/items/{item_id}")
async def upsert_item(
    item_id: str,
    name: Annotated[str | None, Body()] = None,
    size: Annotated[int | None, Body()] = None,
):
    if item_id in items:

from fastapi import FastAPI
from fastapi.testclient import TestClient

swagger_ui_init_oauth = {"clientId": "the-foo-clients", "appName": "The Predendapp"}

app = FastAPI(swagger_ui_init_oauth=swagger_ui_init_oauth)


@app.get("/items/")
async def read_items():
    return {"id": "foo"}


client = TestClient(app)


def test_swagger_ui():
    response = client.get("/docs")
    assert response.status_code == 200, response.text

# Geçmişi, Tasarımı ve Geleceği

Bir süre önce, <a href="https://github.com/fastapi/fastapi/issues/3#issuecomment-454956920" class="external-link" target="_blank">bir **FastAPI** kullanıcısı sordu</a>:

> Bu projenin geçmişi nedir? Birkaç hafta içinde hiçbir yerden harika bir şeye dönüşmüş gibi görünüyor [...]

İşte o geçmişin bir kısmı.

## Alternatifler

from typing import List, Optional, Union

import pytest
from fastapi import FastAPI
from fastapi.exceptions import ResponseValidationError
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    price: Optional[float] = None
    owner_ids: Optional[List[int]] = None


@app.get("/items/invalid", response_model=Item)
def get_invalid():

from typing import Annotated

from fastapi import FastAPI, File, UploadFile
from fastapi.responses import HTMLResponse

app = FastAPI()


@app.post("/files/")
async def create_files(
    files: Annotated[list[bytes], File(description="Multiple files as bytes")],
):
    return {"file_sizes": [len(file) for file in files]}


@app.post("/uploadfiles/")
async def create_upload_files(
    files: Annotated[

from datetime import datetime
from typing import Union

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder
from pydantic import BaseModel

fake_db = {}


class Item(BaseModel):
    title: str
    timestamp: datetime
    description: Union[str, None] = None


app = FastAPI()


@app.put("/items/{id}")
def update_item(id: str, item: Item):
    json_compatible_item_data = jsonable_encoder(item)

---> 100%
Successfully installed fastapi pydantic uvicorn
```

</div>

/// info

📤 🎏 📁 &amp; 🧰 🔬 &amp; ❎ 📦 🔗.

👤 🔜 🎦 👆 🖼 ⚙️ 🎶 ⏪ 📄 🔛. 👶

///

### ✍ **FastAPI** 📟

* ✍ `app` 📁 &amp; ⛔ ⚫️.
* ✍ 🛁 📁 `__init__.py`.
* ✍ `main.py` 📁 ⏮️:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()