How to Fix Decimal Not JSON Serializable Error in Python Lambda Function?

Published: 21 October 2024
on channel: blogize

Summary: Learn the best methods to handle the 'Decimal' not JSON serializable error in AWS Lambda functions using Python. Solve the common issue when dealing with numeric data serialization to JSON.
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How to Fix Decimal Not JSON Serializable Error in Python Lambda Function?

If you're working with AWS Lambda functions and come across the 'Decimal' not JSON serializable error, you're not alone. This error is common when dealing with numeric data that needs to be serialized to JSON. In this guide, we'll explore why this error occurs and how to fix it.

Why Does This Error Occur?

When you use Python's boto3 library with AWS Lambda to interact with services like DynamoDB, you often handle numeric data as Decimal objects. The Decimal type provides precise control over decimal number handling but is not natively supported by Python's default json encoder. This results in a TypeError stating that the object of type 'Decimal' is not JSON serializable.

Solution

To work around this, you need to define a custom encoder that specifies how Decimal objects should be converted to a JSON-compatible format (like a float or str). Below are solutions to help you resolve this issue:

Custom Encoder Method

You can create a custom encoder by subclassing Python's json.JSONEncoder and then using this custom encoder in your JSON serialization process.

[[See Video to Reveal this Text or Code Snippet]]

Lambda Function Context

When you apply this within a Lambda function, you might be processing data and directly needing to return it as a JSON response. Here's how you can incorporate the custom encoder:

[[See Video to Reveal this Text or Code Snippet]]

Summary

The 'Decimal' not JSON serializable error is a common stumbling block when working with numeric data in AWS Lambda using Python, but it can be easily fixed using a custom JSON encoder. By converting Decimal types to float or str, you ensure that your numeric data gets properly serialized to JSON.

Remember to adjust the conversion based on your application's precision needs—whether you convert Decimal to float for ease or to str for precision.

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