在Azure Functions中实现Python依赖注入库遇错求助

在Python Azure Functions中实现依赖注入，选用Dependency Injector库（安装命令：pip install dependency-injector），运行时遇到如下错误：

Error: "unctions.http_app_func. System.Private.CoreLib: Result: Failure
Exception: AttributeError: 'dict' object has no attribute 'encode'"

相关实现代码如下：

function_app.py #

import azure.functions as func
from fastapi import FastAPI, Depends, Request, Response
from dependency_injector.wiring import inject, Provide
from abstraction.di_container import DIContainer
import logging
import json

from src.config.app_settings import AppSettings 

container = DIContainer()
container.wire(modules=[__name__])

fast_app = FastAPI()


@fast_app.exception_handler(Exception)
async def handle_exception(request: Request, exc: Exception):
    return Response(
        status_code=400,
        content={"message": str(exc)},
    )

@fast_app.get("/")
@inject
async def home(settings: AppSettings = Depends(Provide[DIContainer.app_config])):
    cont_name =  settings.get("ContainerName", "No setting found")
    return {
        "info": f"Try to get values from local.settings using DI {cont_name}" 
    }

@fast_app.get("/v1/test/{test}")
async def get_test(self, 
    test: str):
    return {
        "test": test
    }

app = func.AsgiFunctionApp(app=fast_app, http_auth_level=func.AuthLevel.ANONYMOUS)

di_container.py #

from dependency_injector import containers, providers
from src.config.app_settings import AppSettings

class DIContainer(containers.DeclarativeContainer):
    app_config = providers.Singleton(AppSettings)

app_settings.py #

import json
import os
from dependency_injector import containers, providers

class AppSettings:
    def __init__(self, file_path="local.settings.json"):
        self.config_data = {}
        if os.path.exists(file_path):
            with open(file_path, "r", encoding="utf-8") as file:
                data = json.load(file)
                self.config_data = data.get("Values", {})
    
    def get(self, key: str, default=None):
        return os.getenv(key,self.config_data.get(key, default))

错误原因分析 #

1. Response对象使用错误：FastAPI的Response类直接接收dict类型的content时，会尝试调用encode方法编码，但字典没有该方法，触发AttributeError。
2. 路径函数参数冗余：get_test函数中的self参数多余，FastAPI普通路径操作函数无需该参数，会导致请求参数不匹配。

修改步骤 #

1. 修正异常处理器的Response返回：将字典内容序列化为JSON字符串，并指定media_type为application/json。
2. 移除冗余的self参数：删除get_test函数中的self参数。

修改后的关键代码片段 #

# 修正异常处理器
@fast_app.exception_handler(Exception)
async def handle_exception(request: Request, exc: Exception):
    return Response(
        status_code=400,
        content=json.dumps({"message": str(exc)}),
        media_type="application/json"
    )

# 修正get_test函数
@fast_app.get("/v1/test/{test}")
async def get_test(test: str):
    return {
        "test": test
    }

验证说明 #

修改后，依赖注入逻辑保持不变，AppSettings的读取和DIContainer的配置无需调整。运行Azure Functions后，访问相关接口即可正常返回JSON响应，不再触发AttributeError。

内容的提问来源于stack exchange，提问作者Rock