CODEWITHSUNDEEP
pythonjsonpandasserializationlanggraph
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Reputation: 23

TypeError: Object of type NAType is not serializable When Returning a Simple Dictionary in LangGraph

Problem

I'm encountering a TypeError: Object of type NAType is not serializable error while working with LangGraph. This issue arises when invoking the graph, specifically during the return process of a node function. The error persists even when I attempt to return a simple dictionary like {"final_return": "This works"}.

What I'm Trying to Do

I have a node function (final_return_node) that:

  1. Processes a pandas DataFrame from the state object.
  2. Updates the state dictionary with the processed DataFrame using to_dict(orient="records").
  3. Returns a minimal response to simulate a successful state return.

Additionally, I'm using the "Human-in-the-Loop" command interrupt feature from LangGraph, which allows manual interventions during the node execution.

Function Code

import pandas as pd
import numpy as np
import json
from collections.abc import Mapping

def sanitize_state(obj):
    """
    Recursively sanitize the state object to ensure all components are JSON-serializable.
    """
    if isinstance(obj, Mapping):
        return {sanitize_state(key): sanitize_state(value) for key, value in obj.items()}
    
    elif isinstance(obj, (list, tuple, set)):
        return [sanitize_state(item) for item in obj]
    
    elif isinstance(obj, pd.DataFrame):
        return sanitize_state(obj.to_dict(orient="records"))
    
    elif isinstance(obj, pd.Series):
        return sanitize_state(obj.tolist())
    
    elif obj is pd.NA or (isinstance(obj, float) and np.isnan(obj)) or obj is None:
        return None
    
    elif isinstance(obj, (int, float, str, bool)):
        return obj
    
    elif isinstance(obj, (pd.Timestamp, pd.Timedelta)):
        return obj.isoformat() if hasattr(obj, 'isoformat') else str(obj)
    
    elif isinstance(obj, (bytes, bytearray)):
        import base64
        return base64.b64encode(obj).decode('utf-8')
    
    else:
        return str(obj)

def is_json_serializable(obj):
    """
    Check if the object is JSON-serializable.
    """
    try:
        json.dumps(obj)
        return True
    except (TypeError, OverflowError):
        return False

def sanitize_and_verify_state(state):
    """
    Sanitize the state object and verify it's JSON-serializable.
    """
    sanitized = sanitize_state(state)
    
    if not is_json_serializable(sanitized):
        raise ValueError("Sanitized state is not JSON-serializable.")
    
    return sanitized

def final_return_node(self, state):
    print("---MAKING FINAL RETURN---")
    
    state_dict = state.get("keys", {})
    working_data = state_dict.get("working_data", [])
    cmm_input_8 = pd.DataFrame(working_data)
    sanitized_df = cmm_input_8.fillna("").replace({pd.NA: None, np.nan: None})
    
    state["keys"].update({
        "final_return": sanitized_df.to_dict(orient="records"),
    })
    
    print("Completed Final Return, Sanitizing State...")
    
    state = sanitize_and_verify_state(state)
    
    print("Sanitized State Successfully.")
    
    return {"final_return": "This works"}

Observed Behavior

Error Traceback

TypeError                                 Traceback (most recent call last)
...
TypeError: Object of type NAType is not serializable

What I've Tried

  1. Returning a Static Dictionary
    Replaced the function's return with return {"final_return": "This works"}.
    Result: Error persists.

  2. Replacing Missing Values in the DataFrame
    Used fillna("") to replace all missing values with blanks.
    Result: Issue still occurs.

  3. Inspecting the State
    Verified that the state object processes fine during execution.
    Observation: Error arises at the return statement despite sanitizing the DataFrame.

  4. Simplifying the State Update
    Avoided updating the state and returned a static dictionary directly.
    Result: Error still persists.

Environment

Hypothesis

The issue seems to be unrelated to the state or DataFrame itself since the graph executes and processes correctly. It appears to be tied to the return statement and how LangGraph handles the returned data, possibly attempting to serialize the entire state object, which might still contain non-serializable pd.NA values.

Additional Information

Snapshot of the State Before Sanitization

{
    'keys': {
        'original_user_input': 'make cmm input file',
        'uploaded_data': 'BatchSample_USA_Test.csv',
        'uploaded_codebook': None,
        'chat_history': ['Hello, how can I assist?'],
        'node': None,
        'working_data': [
            {
                'Name': 'atch Sample',
                'GroupName': 'SLSP',
                'GroupDescription': 'Property',
                'AnalysisDate': '09/01/2024',
                'Loan': 'Loan AAA',
                'Description': '',
                'Origination': '09/01/2025',
                'Maturity': '09/01/2033',
                'Ownership': nan,  # numpy.nan
                'CurrentOutstandingLoanBalance': 5000000.0,
            },
            # ... more records
        ],
        # ... other keys
    },
    # ... other sections
}

Question

What could be causing LangGraph to raise a TypeError: Object of type NAType is not serializable during a simple dictionary return? Is it an internal LangGraph serialization issue or a misconfiguration on my part? How can I effectively return the entire state to ensure all components are JSON-serializable?

Any assistance would be greatly appreciated!

Upvotes: 0

Views: 64

Answers (0)

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