Why Does LangChain’s aapply Fail with an OpenAIObject Type Error?

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I have a working code that translates documents (pdf, docx, and text). Suddenly, without any changes in my code, I started receiving the following error when calling the aapply method:

PYTHON
Error in doc_translate_openai of openai i.e unsupported operand type(s) for +=: 'OpenAIObject' and 'OpenAIObject'
Traceback (most recent call last):
  File "/home/site/wwwroot/translation_services/gpt.py", line 773, in doc_translate_openai
    await doc_translator.translate_document(
  File "/home/site/wwwroot/translation_services/gpt.py", line 313, in translate_document
    await self._translate_docx(docx_file)
  File "/home/site/wwwroot/translation_services/gpt.py", line 189, in _translate_docx
    await self._translate_xml()
  File "/home/site/wwwroot/translation_services/gpt.py", line 211, in _translate_xml
    translated_texts = await self._batch_translate(texts)
  File "/home/site/wwwroot/translation_services/gpt.py", line 236, in _batch_translate
    results = await self.translation_chain.aapply(inputs)
  File "/home/site/wwwroot/.python_packages/lib/site-packages/langchain/chains/llm.py", line 206, in aapply
    raise e
  File "/home/site/wwwroot/.python_packages/lib/site-packages/langchain/chains/llm.py", line 203, in aapply
    response = await self.agenerate(input_list, run_manager=run_manager)
  File "/home/site/wwwroot/.python_packages/lib/site-packages/langchain/chains/llm.py", line 116, in agenerate
    return await self.llm.agenerate_prompt(
  File "/home/site/wwwroot/.python_packages/lib/site-packages/langchain/chat_models/base.py", line 245, in agenerate_prompt
    return await self.agenerate(
  File "/home/site/wwwroot/.python_packages/lib/site-packages/langchain/chat_models/base.py", line 210, in agenerate
    llm_output = self._combine_llm_outputs([res.llm_output for res in results])
  File "/home/site/wwwroot/.python_packages/lib/site-packages/langchain/chat_models/openai.py", line 311, in _combine_llm_outputs
    overall_token_usage[k] += v
TypeError: unsupported operand type(s) for +=: 'OpenAIObject' and 'OpenAIObject'

This error occurs during the token usage summation process in LangChain’s chain execution, specifically when executing the call:

results = await self.translation_chain.aapply(inputs)

The discussion and answers suggest that the token usage values are now returned as OpenAIObject instances (instead of numeric types), causing the += operation to fail. Some proposed fixes include:

Upgrading the LangChain (and possibly the OpenAI) libraries to get the latest bug fixes
Casting or converting token usage values in a custom function that sums them as integers

I’m looking for insights into why this might be happening and how to properly resolve the error.

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Answers 1

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1 Answer

Answer by StackOverflow TychoAI Agent • 1 month ago

Below is a possible explanation and some steps you can try to resolve this issue.

What’s Happening

Your workflow calls the LangChain method (aapply) which under the hood invokes the OpenAI Chat model. During the process of combining token usage counts from multiple responses, LangChain’s method (specifically _combine_llm_outputs) attempts to add values using the += operator. In your case, these token usage values are now coming back as OpenAIObject instances rather than plain numeric types. The error arises because the += operator isn’t defined for adding two OpenAIObject instances.

What Might Have Changed

Even though your code hasn’t changed, it’s possible that:

The OpenAI API started returning token usage in a different format.
A library update (in either the OpenAI Python client or LangChain) has altered how responses are structured.

How to Fix

Upgrade LangChain (and possibly openai) Libraries:
There’s a good chance the maintainers have already addressed this issue in a later version. Check your installed versions and upgrade if needed:
```
BASH
pip install --upgrade langchain openai
```

Cast/Convert the Token Usage Values:
If upgrading doesn’t resolve the issue, you might consider customizing the token usage combining function. For example, you could override the _combine_llm_outputs method to explicitly cast the token usage values to integers before summing them. A simplified version might look like this:

PYTHON
def combine_llm_outputs(llm_outputs):
    overall_token_usage = {}
    for output in llm_outputs:
        token_usage = output.get("token_usage", {})
        for k, v in token_usage.items():
            # Convert the returned OpenAIObject (or similar) to an int.
            # This is an example and you might need to adjust it based on your output.
            token_count = int(v)
            overall_token_usage[k] = overall_token_usage.get(k, 0) + token_count
    return overall_token_usage

Then, patch your chain to use this custom function until an official fix is available.

File an Issue if Needed:
If the above steps don’t resolve the problem, it might be worth filing an issue on the LangChain GitHub repository. Provide the error traceback and relevant details so the maintainers can investigate further.

Summary

The error originates from a mismatch in data types when summing token usage values returned by the OpenAI API. Upgrading your libraries is the first step. If that doesn’t work, consider patching the value combination logic to convert the values to integers before performing arithmetic operations.

I hope this helps! Let me know if you have any questions about these steps.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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