FastAPI: প্রথম API

uv init notes-api && cd notes-api
uv add "fastapi[standard]"

# main.py
from fastapi import FastAPI

app = FastAPI(title="Notes API", version="0.1.0")


@app.get("/")
async def root():
    return {"message": "স্বাগতম!"}


@app.get("/hello/{name}")
async def hello(name: str, times: int = 1):
    return {"greeting": f"হ্যালো {name}! " * times}

uv run fastapi dev main.py

from fastapi import FastAPI, Header, Query
from pydantic import BaseModel, Field

app = FastAPI()


class NoteCreate(BaseModel):
    title: str = Field(min_length=1, max_length=200)
    content: str = ""
    tags: list[str] = []


@app.post("/notes/{folder_id}")
async def create_note(
    folder_id: int,                                   # path এ আছে → path parameter
    note: NoteCreate,                                 # Pydantic model → JSON body
    pin: bool = False,                                # সাধারণ type, path এ নেই → query (?pin=true)
    lang: str = Query("bn", pattern="^(bn|en)$"),     # query, যাচাইসহ
    user_agent: str | None = Header(None),            # header
):
    return {"folder": folder_id, "note": note, "pin": pin, "lang": lang, "ua": user_agent}

{
  "detail": [
    {
      "type": "int_parsing",
      "loc": ["path", "folder_id"],
      "msg": "Input should be a valid integer, unable to parse string as an integer",
      "input": "abc"
    }
  ]
}

from datetime import datetime
from fastapi import FastAPI, HTTPException, status
from pydantic import BaseModel, Field

app = FastAPI()


class NoteCreate(BaseModel):
    title: str = Field(min_length=1, max_length=200)
    content: str = ""


class NoteOut(BaseModel):
    id: int
    title: str
    content: str
    created_at: datetime


# আপাতত memory তে রাখছি; পরের অধ্যায়ে database
_notes: dict[int, dict] = {}
_next_id = 1


@app.post("/notes", response_model=NoteOut, status_code=status.HTTP_201_CREATED)
async def create_note(data: NoteCreate):
    global _next_id
    note = {"id": _next_id, **data.model_dump(), "created_at": datetime.now(), "owner_secret": "xyz"}
    _notes[_next_id] = note
    _next_id += 1
    return note          # owner_secret বাদ পড়বে, কারণ NoteOut এ নেই


@app.get("/notes", response_model=list[NoteOut])
async def list_notes(limit: int = 20, offset: int = 0):
    return list(_notes.values())[offset : offset + limit]


@app.get("/notes/{note_id}", response_model=NoteOut)
async def get_note(note_id: int):
    note = _notes.get(note_id)
    if note is None:
        raise HTTPException(status_code=404, detail="Note পাওয়া যায়নি")
    return note


@app.delete("/notes/{note_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_note(note_id: int):
    if _notes.pop(note_id, None) is None:
        raise HTTPException(status_code=404, detail="Note পাওয়া যায়নি")

from typing import Annotated
from fastapi import Depends


class Pagination(BaseModel):
    limit: int
    offset: int


def pagination(limit: int = Query(20, ge=1, le=100), offset: int = Query(0, ge=0)) -> Pagination:
    return Pagination(limit=limit, offset=offset)


PageDep = Annotated[Pagination, Depends(pagination)]


@app.get("/notes")
async def list_notes(page: PageDep):
    return list(_notes.values())[page.offset : page.offset + page.limit]

@app.get("/a")
async def a():          # event loop এ চলে; ভেতরে শুধু await করা I/O
    ...

@app.get("/b")
def b():                # FastAPI আলাদা thread এ চালায়; sync library চলে
    ...

from fastapi.middleware.cors import CORSMiddleware

app.add_middleware(
    CORSMiddleware,
    allow_origins=["https://app.example.com", "http://localhost:3000"],   # "*" production এ না
    allow_methods=["*"],
    allow_headers=["*"],
    allow_credentials=True,
)