Resolving TypeError in Python Requests While Uploading Files from S3 to an API Endpoint

Learn how to fix the intermittent `TypeError` when using the Python `requests` library to upload files from S3 to an API. This guide provides step-by-step solutions and code examples.
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Fixing the TypeError in Python Requests When Uploading from S3

Working with files stored in Amazon S3 and sending them as multipart requests to an API can be tricky. Developers often encounter various issues, especially when handling file uploads in Python. In this post, we'll dive into one common problem: a TypeError that appears intermittently when using the requests library to post files retrieved from S3. We'll explore the root of the issue and provide a solution to get your application working smoothly.

Understanding the Problem

When attempting to upload a file from S3 to another service using multipart requests, you may encounter an error message like this:

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

How Does the Code Work?

The initial code structure contains a few functions that manage the process of retrieving a file from S3 and sending it as a multipart request.

Main Execution Function: This function processes an event and checks if the required emailId is present before proceeding to download the file and initiate the upload.

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

Download Function: This function retrieves the specified file from S3 and returns it for later use.

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

Multipart Request Function: This function handles the actual upload of the file to the specified endpoint.

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

Identifying the Issue

The error occurs because of the way file content is being processed. Specifically, the file_content needs to be a bytes-like object, whereas the way the files dictionary was structured may not fulfill that requirement.

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

Solution: Fixing the TypeError

To resolve the TypeError, we can make a few adjustments to the existing code. Here’s a revised version with detailed steps:

Step 1: Update the Download Function

Change the download_s3_file_to_tmp function to return the content of the file as a string, ensuring you read the opened file properly.

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

Step 2: Modify the Multipart Request Function

Adjust the multipart request handler to accept and correctly format the file content:

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

Summary of Changes

The reading of the file in binary mode ensures you get the correct bytes-like object for uploading.

The files structure now specifies a tuple with the proper names and the type of content for accurate multipart handling.

Conclusion

Give it a try in your setup, and feel free to share your insights or any further questions!