AWS Lambda中lambda_handler缺少event和context参数报错求助

核心错误原因 #

从错误日志的栈追踪可以明确定位问题：

File "/var/task/lambda_function.py", line 80, in <module>
    lambda_handler()

你的代码在模块顶层（所有函数定义之外）直接调用了lambda_handler()，但这个函数要求传入event和context两个必填参数，无参调用直接触发TypeError。而且这个调用会在Lambda加载代码模块的初始化阶段执行，直接导致函数初始化失败。

第一步：修复直接调用问题 #

删除代码中模块顶层的lambda_handler()调用语句（即报错指向的第80行）。Lambda会在触发时自动调用lambda_handler并传入event和context参数，完全不需要手动调用。

第二步：修复代码中的其他潜在问题 #

除了核心报错，你的代码还有几个会导致后续运行失败的问题，需要一并修正：

1. DynamoDB使用错误 #

当前代码中，dynamodb.Table()返回Table对象但未赋值，后续直接用dynamodb.get_item()是错误的，且get_item的返回数据嵌套在Item键下：

# 错误写法
dynamodb = boto3.resource("dynamodb")
dynamodb.Table("woolyquant_cria_trading_bot")
dynamodb_item = dynamodb.get_item(...)

# 修正后
dynamodb = boto3.resource("dynamodb")
table = dynamodb.Table("woolyquant_cria_trading_bot")
dynamodb_response = table.get_item(
    Key = {
        'Date': yesterday[0:10],
        'TickerSymbol': ticker,
    }
)
# 处理找不到数据的情况
if 'Item' not in dynamodb_response:
    return {"statusCode": 404, "body": "目标数据不存在"}
prev_closing_price = fast_atof(dynamodb_response['Item']['ClosingPrice'])

2. requests响应处理错误 #

get_current_asset_position函数中，requests.get()返回的是Response对象而非字典，需要调用.json()解析，同时建议添加HTTP错误捕获：

def get_current_asset_position(ticker: str) -> dict:
    url = f'https://paper-api.alpaca.markets/v2/positions/{ticker}'
    
    headers = {
        "accept": "application/json",
        "content-type": "application/json",
        "APCA-API-KEY-ID": ALPACA_CONFIG['API_KEY'],
        "APCA-API-SECRET-KEY": ALPACA_CONFIG['API_SECRET']
    }
    
    response = requests.get(url, headers=headers)
    response.raise_for_status()  # 自动抛出HTTP错误
    return response.json()

3. Alpaca订单Payload占位符未替换 #

alpaca_payload中的"string"占位符（如"notional": "string"）是无效值，Alpaca API会拒绝此类请求。需要根据订单类型调整参数，比如止损单必须包含stop_price：

alpaca_payload = {
    "symbol": "AAPL",
    "type": "stop",
    "time_in_force": "day",
    "extended_hours": False,
    # 补充止损价示例，根据策略调整
    "stop_price": str(curr_price * 0.98)
}

修复后的完整代码示例 #

import os
import boto3
import ctypes
import logging
from datetime import datetime
from datetime import timedelta
from config import ALPACA_CONFIG

import requests

# Handle fast str -> float conversion
def fast_atof(s) -> float:
    return ctypes.c_float(float(s)).value


def get_current_asset_position(ticker: str) -> dict:
    url = f'https://paper-api.alpaca.markets/v2/positions/{ticker}'
    
    headers = {
        "accept": "application/json",
        "content-type": "application/json",
        "APCA-API-KEY-ID": ALPACA_CONFIG['API_KEY'],
        "APCA-API-SECRET-KEY": ALPACA_CONFIG['API_SECRET']
    }
    
    response = requests.get(url, headers=headers)
    response.raise_for_status()
    return response.json()


def lambda_handler(event, context):
    url = "https://paper-api.alpaca.markets/v2/orders"
    ticker = "AAPL"
    yesterday = str(datetime.today() - timedelta(days = 1))
    
    dynamodb = boto3.resource("dynamodb")
    table = dynamodb.Table("woolyquant_cria_trading_bot")
    dynamodb_response = table.get_item(
        Key = {
            'Date': yesterday[0:10],
            'TickerSymbol': ticker,
        }
    )
    
    if 'Item' not in dynamodb_response:
        return {"statusCode": 404, "body": f"{ticker}在{yesterday[0:10]}无数据记录"}

    alpaca_headers = {
        "accept": "application/json",
        "content-type": "application/json",
        "APCA-API-KEY-ID": ALPACA_CONFIG['API_KEY'],
        "APCA-API-SECRET-KEY": ALPACA_CONFIG['API_SECRET']
    }
    
    alpaca_payload = {
        "symbol": "AAPL",
        "type": "stop",
        "time_in_force": "day",
        "extended_hours": False,
    }
    
    asset = get_current_asset_position(ticker=ticker)
    prev_closing_price = fast_atof(dynamodb_response['Item']['ClosingPrice'])
    curr_price = fast_atof(asset['current_price'])
    
    if curr_price > prev_closing_price * 1.05:
        alpaca_payload['qty'] = asset['qty']
        alpaca_payload['side'] = 'sell'
        alpaca_payload['stop_price'] = str(curr_price * 0.98)
        
        response = requests.post(url, json=alpaca_payload, headers=alpaca_headers)
        response.raise_for_status()
        return {"statusCode": 200, "body": response.json()}
    
    if curr_price < prev_closing_price * 0.8995:
        alpaca_payload['qty'] = '10'
        alpaca_payload['side'] = 'buy'
        alpaca_payload['stop_price'] = str(curr_price * 1.02)
        
        response = requests.post(url, json=alpaca_payload, headers=alpaca_headers)
        response.raise_for_status()
        return {"statusCode": 200, "body": response.json()}
    
    return {"statusCode": 200, "body": "未触发交易条件"}

总结 #

1. 优先删除模块顶层的lambda_handler()调用，这是当前报错的直接原因；
2. 修正DynamoDB和requests的使用逻辑，确保数据能正确读取与解析；
3. 清理Alpaca订单参数中的无效占位符，符合API要求。

内容的提问来源于stack exchange，提问作者Jonathan Grady