backend-utils

Useful python tools for backend services

Documentation

Tools

• Singleton - metaclass to make singletons

from backend_utils.tools import Singleton

class A(metaclass=Singleton):
    pass

print(id(A()) == id(A())) # True

• StrEnum - subclasses that create variants using auto() will have values equal to their names

from enum import auto

from backend_utils.tools import StrEnum

class Bit(StrEnum):
    one = auto()
    two = auto()

print(Bit.one.value) # 'one'
print(Bit.two.value) # 'two'

Server

• Router, compile_routers, register_routers - build routers for fastapi app

from fastapi import FastAPI, APIRouter

from backend_utils.server import (
    Router, compile_routers, register_routers
)
router = APIRouter()

routers = [
    Router(router=router, tags=['Users'], prefix='/users'),
]


compiled_routers = compile_routers(
    routers=routers,
    root_prefix='/api/v1'
)

app = FastAPI()
register_routers(
    app=app,
    routers=[*compiled_routers]
)

This code will compile routers: /api/v1/users/*

Http

• RequestMethods - enum for http methods

• BaseRequester - base class for http clients. You can specify URL, TIMEOUT, MIDDLEWARE. Use self.make_request() to make http requests

import os
import asyncio
from typing import Optional

import httpx
from backend_utils.http import BaseRequester, RequestMethods


class JsonPlaceholder(BaseRequester):
    URL = os.getenv('JSONPLACEHOLDER_URL', 'https://jsonplaceholder.typicode.com')
    TIMEOUT = 10

    async def get_todo(self, todo_id: int) -> Optional[httpx.Response]:
        return await self.make_request(
            method=RequestMethods.GET,
            uri=f'/todos/{todo_id}',
        )

    
if __name__ == '__main__':
    jp = JsonPlaceholder()
    asyncio.run(jp.get_todo(todo_id=1))

You also can validate response with pydantic models

import os
import asyncio
from typing import Optional

from pydantic import BaseModel, Field
from backend_utils.http import BaseRequester, RequestMethods

class GetTodo(BaseModel):
    user_id: int = Field(..., alias='userId')
    id: int
    title: str
    completed: bool

class JsonPlaceholder(BaseRequester):
    async def get_todo_model(self, todo_id: int) -> Optional[GetTodo]:
        url = os.getenv('JSONPLACEHOLDER_URL', 'https://jsonplaceholder.typicode.com')
        return await self.make_request(
            method=RequestMethods.GET,
            url=f'{url}/todos/{todo_id}',
            response_model=GetTodo,
            timeout=5.5
        )

    
if __name__ == '__main__':
    jp = JsonPlaceholder()
    asyncio.run(jp.get_todo_model(todo_id=1))

So it will return GetTodo model or None if request failed

• BaseMiddleware - base class for http request middleware. Available methods:
  • before_request(self, request: httpx.Request)
  • after_request(self, request: httpx.Request, response: httpx.Response):
  • on_request_error(self, request: httpx.Request, error: httpx.HTTPError)
  • on_request_status_error(self, request: httpx.Request)
  • on_validation_error(self, response: httpx.Response, error: [ValidationError, json.decoder.JSONDecodeError])

For example middleware to print request time

import os
import time
import asyncio
from typing import Optional

import httpx
from backend_utils.http import BaseRequester, RequestMethods, BaseMiddleware


class PrintRequestTime(BaseMiddleware):
    async def before_request(self, request: httpx.Request):
        request.start_time = time.perf_counter()

    async def after_request(self, request: httpx.Request, response: httpx.Response):
        request_time = time.perf_counter() - request.start_time
        print(request_time)


class JsonPlaceholder(BaseRequester):
    URL = os.getenv('JSONPLACEHOLDER_URL', 'https://jsonplaceholder.typicode.com')
    MIDDLEWARES = [PrintRequestTime()]
    
    async def get_todo(self, todo_id: int) -> Optional[httpx.Response]:
        return await self.make_request(
            method=RequestMethods.GET,
            uri=f'/todos/{todo_id}',
        )

    
if __name__ == '__main__':
    jp = JsonPlaceholder()
    asyncio.run(jp.get_todo(todo_id=1))