调用API填充Python列表遇JSONDecodeError，未超限却49000条时报错

Hey there! Let's dig into why you're hitting that JSONDecodeError: Expecting value: line 1 column 1 (char 0) exactly when you reach 49000 results, even though you're sticking to the API's stated rate limits (500 items per request, 200 requests per minute). Here are the most likely causes and actionable fixes:

Common Causes & Solutions #

1. API Returned Non-JSON Content (Hidden Rate Limiting or Error) #

Even if you're counting requests correctly, APIs sometimes have unpublished or granular limits (like per-second request caps or cumulative request thresholds) that trigger non-JSON responses when exceeded. At the 49000 mark, that's your 98th request (49000 / 500 = 98), which might hit a hidden limit you didn't account for. Instead of returning a valid JSON error, the API could send an HTML error page, blank text, or a plaintext "too many requests" message—none of which can be parsed as JSON.

Fixes:

• Add a status code check before parsing to catch errors early:

  response = requests.get(api_url, params=your_params)
  if response.status_code != 200:
      print(f"Request failed with status {response.status_code}: {response.text}")
      # Handle error (retry, log, etc.)
      continue
  

• Wrap JSON parsing in a try-except block to capture failures and save the raw response for debugging:

  import json
  
  try:
      data = response.json()
  except json.JSONDecodeError as e:
      with open("failed_response.txt", "w") as f:
          f.write(response.text)
      print(f"Failed to parse JSON. Saved response to failed_response.txt: {e}")
      # Retry or exit gracefully
  

2. Network Fluctuations Caused Truncated/Empty Responses #

Network blips can strike randomly, and at the 98th request, you might have received an incomplete or empty response. The error message "Expecting value: line 1 column 1" is a dead giveaway that the parser got nothing (or garbage) instead of valid JSON.

Fixes:

• Implement a retry mechanism with exponential backoff to handle transient issues:

  import time
  
  max_retries = 3
  retries = 0
  while retries < max_retries:
      try:
          response = requests.get(api_url, params=your_params)
          response.raise_for_status()  # Triggers exception for 4xx/5xx statuses
          data = response.json()
          break
      except (requests.exceptions.RequestException, json.JSONDecodeError):
          retries += 1
          time.sleep(2 ** retries)  # Exponential backoff: 2s, 4s, 8s
  else:
      print(f"Failed after {max_retries} retries")
  

• Check if the response content is empty before parsing:

  if not response.content:
      print("Received empty response—likely a network issue")
      # Retry or skip this request
  

3. Broken Pagination Logic #

If you're using offset-based pagination (e.g., ?offset=48500 for the 98th request), some APIs have hard limits on how high the offset can go. After a certain point, they might return malformed JSON or an empty response instead of a proper "no more data" message. Alternatively, if you're using cursor-based pagination, you might have missed updating the cursor correctly for a page, leading to an invalid request.

Fixes:

• Verify your pagination parameters: Ensure you're correctly incrementing the offset by 500 each time, or that you're using the next_cursor (or similar) value returned in the API's response for the next page.
• Check the API documentation for a maximum offset limit—some cap it at 50,000 items, which would align perfectly with your 49000 cutoff.

4. Insufficient Request Delay #

Even if you're under the 200 requests per minute limit, sending requests too quickly (e.g., 200 requests in the first 10 seconds of the minute) can trigger rate limiting. Some APIs enforce per-second caps to prevent burst traffic, which might not be listed in the official docs.

Fix:

• Add a small delay between requests to spread them out evenly:

  import time
  
  # After each successful request
  time.sleep(0.3)  # 300ms delay ensures ~200 requests per minute (60 / 0.3 = 200)
  

内容的提问来源于stack exchange，提问作者gerlof92