FastAPI Minimal CRUD Template

main.py

"""FastAPI Minimal CRUD Template

```bash
uv add 'fastapi[standard]'
# Paste this file into main.py
uv run fastapi dev
```

```bash
curl -X GET http://localhost:8000/api/todos
curl -X GET http://localhost:8000/api/todos/N
curl -X POST -H 'content-type: application/json' -d '{"title": "new todo"}' http://localhost:8000/api/todos
curl -X PUT -H 'content-type: application/json' -d '{"title": "updated todo", "status": "IN_PROGRESS"}' http://localhost:8000/api/todos/N
curl -X DELETE http://localhost:8000/api/todos/N
```
"""
from enum import StrEnum

from fastapi import FastAPI, status
from fastapi.exceptions import HTTPException
from pydantic import BaseModel as _BaseModel
from pydantic import ConfigDict

IN_MEMORY_DB: dict[int, Todo] = {}


class Status(StrEnum):
    NEW = "NEW"
    IN_PROGRESS = "IN_PROGRESS"
    COMPLETED = "COMPLETED"


class BaseModel(_BaseModel):
    model_config = ConfigDict(frozen=True)


class Todo(BaseModel):
    id: int
    title: str
    status: Status


class ListTodosResponse(BaseModel):
    todos: list[Todo]


class CreateTodoRequest(BaseModel):
    title: str


class UpdateTodoRequest(BaseModel):
    title: str
    status: Status


app = FastAPI()


@app.get("/")
async def index() -> dict:
    return {"message": "hello"}


@app.get("/api/todos")
async def list_todos() -> ListTodosResponse:
    return ListTodosResponse(todos=[todo for todo in IN_MEMORY_DB.values()])


@app.post("/api/todos", status_code=status.HTTP_201_CREATED)
async def create_todo(data: CreateTodoRequest) -> Todo:
    next_id = max(IN_MEMORY_DB) + 1 if IN_MEMORY_DB else 0
    todo = Todo(id=next_id, title=data.title, status=Status.NEW)
    IN_MEMORY_DB[next_id] = todo
    return todo


@app.get("/api/todos/{todo_id}")
async def get_todo(todo_id: int) -> Todo:
    todo = IN_MEMORY_DB.get(todo_id, None)
    if not todo:
        raise HTTPException(404)

    return todo


@app.put("/api/todos/{todo_id}")
async def update_todo(todo_id: int, data: UpdateTodoRequest) -> Todo:
    todo = IN_MEMORY_DB.pop(todo_id, None)
    if not todo:
        raise HTTPException(404)

    new_todo = todo.model_copy(update=dict(title=data.title, status=data.status))

    IN_MEMORY_DB[todo.id] = new_todo

    return new_todo


@app.delete("/api/todos/{todo_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_todo(todo_id: int) -> None:
    if todo_id in IN_MEMORY_DB:
        del IN_MEMORY_DB[todo_id]

    return None