深入理解Python requests.post 参数与循环中断机制

import requests

def retry_post_problematic(url, data, headers, max_retries=3):
  for retry in range(max_retries):
    try:
      response = requests.post(url, data, headers) # 问题所在：参数传递不当
      if response.status_code == 200:
        break # 预期在成功时中断循环
      else:
        print(f"Request failed with status code {response.status_code}. Retrying...")
    except (requests.exceptions.RequestException, Exception): # 问题所在：未捕获异常对象
      print(f"Request failed with exception: {e}. Retrying...") # 无法访问 e
  if response.status_code != 200:
    raise RuntimeError("Max retries exceeded.")
  return response

import requests
import time # 引入 time 模块用于实现重试间隔

def retry_post_robust(url, data, headers, max_retries=3, initial_delay=1):
    """
    对 requests.post 请求进行重试的函数。

    Args:
        url (str): 请求的URL。
        data (dict/str): 请求体数据。
        headers (dict): 请求头。
        max_retries (int): 最大重试次数。
        initial_delay (int): 首次重试前的等待秒数。

    Returns:
        requests.Response: 成功的响应对象。

    Raises:
        RuntimeError: 如果达到最大重试次数后请求仍未成功。
    """
    response = None # 初始化 response
    for retry_count in range(max_retries):
        try:
            # 关键修正：使用关键字参数明确传递 data 和 headers
            response = requests.post(url, data=data, headers=headers)
            if response.status_code == 200:
                print(f"Request successful on attempt {retry_count + 1}.")
                break # 请求成功，中断循环
            else:
                print(f"Attempt {retry_count + 1}: Request failed with status code {response.status_code}. Retrying...")
        except requests.exceptions.RequestException as e:
            # 关键修正：捕获具体的 RequestException 并记录异常信息
            print(f"Attempt {retry_count + 1}: Request failed with network exception: {e}. Retrying...")
        except Exception as e:
            # 捕获其他未知异常
            print(f"Attempt {retry_count + 1}: Request failed with unexpected exception: {e}. Retrying...")

        # 如果不是最后一次尝试，则进行等待
        if retry_count < max_retries - 1:
            # 可以添加指数退避策略，这里简化为固定延迟
            time.sleep(initial_delay * (2 ** retry_count)) # 示例：指数退避
        else:
            print("Max retries reached.")

    # 循环结束后检查最终状态
    if response is None or response.status_code != 200:
        raise RuntimeError(f"Max retries ({max_retries}) exceeded. Last status: {response.status_code if response else 'N/A'}")

    return response

# 示例用法
if __name__ == "__main__":
    test_url = "https://httpbin.org/post" # 一个用于测试 POST 请求的公共服务
    test_data = {"key": "value", "message": "hello world"}
    test_headers = {"Content-Type": "application/x-www-form-urlencoded"} # 或 "application/json"

    print("--- 尝试一个预期成功的请求 ---")
    try:
        successful_response = retry_post_robust(test_url, test_data, test_headers, max_retries=3)
        print(f"最终请求成功，状态码: {successful_response.status_code}, 响应内容: {successful_response.json()}")
    except RuntimeError as e:
        print(f"请求失败: {e}")

    print("\n--- 尝试一个预期失败的请求 (模拟网络错误或服务器错误) ---")
    # 为了模拟失败，我们可以尝试一个不存在的URL或者一个会返回错误的URL
    # 这里我们使用一个故意错误的URL来触发异常
    error_url = "http://nonexistent-domain.com/post" 
    try:
        failed_response = retry_post_robust(error_url, test_data, test_headers, max_retries=2, initial_delay=0.1)
        print(f"最终请求成功，状态码: {failed_response.status_code}")
    except RuntimeError as e:
        print(f"请求失败: {e}")
    except requests.exceptions.ConnectionError as e:
        print(f"请求失败，连接错误: {e}")

    print("\n--- 尝试一个预期失败但状态码非200的请求 ---")
    # 模拟一个总是返回非200状态码的API
    bad_status_url = "https://httpbin.org/status/400"
    try:
        bad_status_response = retry_post_robust(bad_status_url, test_data, test_headers, max_retries=2, initial_delay=0.1)
        print(f"最终请求成功，状态码: {bad_status_response.status_code}")
    except RuntimeError as e:
        print(f"请求失败: {e}")