Handling Errors with aiohttp ClientResponseError

Feb 22, 2024 ยท 2 min read

When making requests with the aiohttp client library in Python, you may occasionally run into ClientResponseError exceptions. These indicate that there was an HTTP error response from the server.

What Causes a ClientResponseError

Common causes of ClientResponseError include:

  • The server returned a 4xx client error - like 400 Bad Request or 404 Not Found
  • The server returned a 5xx server error - like 500 Internal Server Error
  • There was an exception while receiving the response data
  • For example:

    async with aiohttp.ClientSession() as session:
      async with session.get('http://example.com/invalid') as resp:
        text = await resp.text() # ClientResponseError raised here

    So how do we properly handle these errors?

    Checking the Status Code

    The ClientResponseError contains the status code that was returned. You can access it through the status attribute:

      async with session.get(url) as resp:
        await resp.text()
    except aiohttp.ClientResponseError as e:
      print(e.status) # Print status code
      print(e.message) # Print error message

    This allows you to check the status code and handle different cases differently.

    Accessing the Response

    Even though there was an error, you can still access the response object through the response attribute on the exception:

    resp = e.response
    print(resp.headers) # Print headers

    This allows you to extract additional debug information from the response.

    Key Takeaways

  • ClientResponseError happens on 4xx/5xx status codes or response read issues
  • Check e.status to identify the status code
  • Access the response via e.response for more debugging info
  • Handle different status codes differently in your exception handling
  • Properly handling these client-side errors ensures your aiohttp application is robust and user-friendly.

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