Скачать или смотреть Extracting Filenames from S3: A Step-by-Step Guide Using S3Hook

Learn how to effortlessly get only the `filenames` from Amazon S3 using S3Hook in Airflow, streamlining your data handling process.
---
This video is based on the question https://stackoverflow.com/q/66922255/ asked by the user 'KristiLuna' ( https://stackoverflow.com/u/14444816/ ) and on the answer https://stackoverflow.com/a/66923450/ provided by the user 'Alan Ma' ( https://stackoverflow.com/u/1464966/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Get only the filename from s3 using s3hook

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Extracting Filenames from S3: A Step-by-Step Guide Using S3Hook

When working with Amazon S3, one common challenge developers face is the need to manipulate filenames within S3 buckets. In this guide, we'll dive into a specific use case: How to extract the actual filenames from an S3 directory when copying files from one location to another. This task is particularly relevant for developers using Apache Airflow with S3Hook to manage their workflows efficiently. Let’s explore how to tackle this problem effectively.

The Problem: Extracting Filenames

Imagine you have a folder structure in your S3 bucket that contains files like this:

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

You need to copy these files to a new directory while keeping only their names for the destination. The goal is to have a new path as follows:

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

The challenge here is extracting just the filename from the full path while ensuring that the new path is correctly formatted in your code.

Understanding the S3 Structure

Before we jump into the solution, it’s important to note that S3 treats the path as a part of the filename. Thus, there’s no actual file system hierarchy in S3; the paths are effectively prefixes for the object names. This means that to extract just the filename, we need to manipulate the string accordingly.

The Solution Steps

Step 1: List the Objects in S3

Using the S3Hook, we can connect to our S3 bucket and list all the keys (files) that match a specific prefix. Here’s a quick look at how that works in Python:

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

In this snippet, self.partition.bucket specifies your S3 bucket, while self.partition.key_prefix refers to the folder from which you're copying files.

Step 2: Extract the Filenames

Now, for each key retrieved, we can split the string to get the filename. Python's os.path.split() function is handy here. This function separates the directory path from the filename:

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

The variable filename will now have only the actual name of the file (like my_unique_filename.csv).

Step 3: Build the Destination Key

With the filename extracted, we can now construct the destination key (new location) by appending the filename to the new prefix. Here’s how to do it:

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

In this case, self.dest_prefix would be your new directory, such as new_folder1.

Step 4: Copy and Delete Objects

Next, perform the copy operation using the constructed destination key, and afterward, delete the original files if necessary:

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

This code handles each object in the S3 bucket, copying it from the source to the destination and cleaning up the original files as needed.

Put it All Together

Finally, here's the complete code snippet that combines all the steps we've discussed:

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

Conclusion

By following this guide, you can effectively extract filenames from S3 and use them in your workflows. Whether you're managing large datasets or simply organizing files, this method streamlines the process and ensures your data remains tidy. Now, you can confidently manipulate S3 filenames within your Apache Airflow tasks!