Introduction to s3transfer

The s3transfer library is a module by AWS that facilitates high-level management of Amazon S3 transfers in Python applications. It provides a robust interface for uploading and downloading files with optimized strategies, making it suitable for developers integrating S3 operations in their applications. In this guide, we will explore the s3transfer library, its useful APIs, and practical code examples, concluding with an app example utilizing them. Let’s delve in!

Key Features of s3transfer

Before we dive into the APIs, let’s highlight some of the features of s3transfer:

• Optimized handling of multipart uploads and downloads.
• Automatic retries and failure recovery mechanisms.
• Advanced options for managing concurrency.

API Examples

Here are some useful APIs provided by s3transfer along with examples:

1. Uploading a File

Uploading files to S3 is made seamless with the upload_file() method:

  from s3transfer import S3Transfer
  import boto3

  client = boto3.client('s3')
  transfer = S3Transfer(client)
  
  # Upload a file
  transfer.upload_file('local_file.txt', 'my-bucket', 'remote_file.txt')
  print("File uploaded successfully!")

2. Downloading a File

To download a file from S3, the download_file() method is highly efficient:

  # Download a file
  transfer.download_file('my-bucket', 'remote_file.txt', 'local_file.txt')
  print("File downloaded successfully!")

3. Setting Custom Transfer Configuration

Customize transfer options such as concurrency with s3transfer.TransferConfig:

  from s3transfer import TransferConfig

  # Define a custom configuration
  config = TransferConfig(
      multipart_threshold=10*1024*1024, # Multipart upload threshold
      max_concurrency=10                # Maximum concurrency
  )
  
  # Upload with custom configuration
  transfer.upload_file('local_file_large.txt', 'my-bucket', 
                       'remote_file_large.txt', 
                       extra_args=None, 
                       callback=None, 
                       config=config)
  print("File uploaded with custom config!")

4. Tracking Progress with a Callback

Add a progress callback function to monitor uploads/downloads:

  def progress_callback(bytes_transferred):
      print(f"{bytes_transferred} bytes transferred.")

  # Transfer with a progress callback
  transfer.upload_file('large_file.txt', 'my-bucket', 'uploaded_file.txt', 
                       callback=progress_callback)

5. Deleting Multiple Files

While s3transfer itself doesn’t provide a dedicated delete method, you can use related boto3 functionalities:

  objects_to_delete = {'Objects': [{'Key': 'file1.txt'}, {'Key': 'file2.txt'}]}
  client.delete_objects(Bucket='my-bucket', Delete=objects_to_delete)
  print("Files deleted successfully!")

Building an Example App with s3transfer

Here’s an example of building a simple Python script that integrates these APIs for a file transfer application:

  from s3transfer import S3Transfer, TransferConfig
  import boto3

  client = boto3.client('s3')
  transfer = S3Transfer(client)
  
  def upload_file(file_name, bucket_name, object_name, config):
      transfer.upload_file(file_name, bucket_name, object_name, config=config)
      print(f"Uploaded: {file_name}")

  def download_file(bucket_name, object_name, file_name):
      transfer.download_file(bucket_name, object_name, file_name)
      print(f"Downloaded: {file_name}")

  def list_files(bucket_name):
      response = client.list_objects_v2(Bucket=bucket_name)
      print("Files in bucket:")
      for content in response.get('Contents', []):
          print(content['Key'])

  # Configuration
  custom_config = TransferConfig(multipart_threshold=8*1024*1024, max_concurrency=4)

  if __name__ == "__main__":
      upload_file('sample.txt', 'my-bucket', 'sample.txt', custom_config)
      download_file('my-bucket', 'sample.txt', 'downloaded_sample.txt')
      list_files('my-bucket')

Conclusion

The s3transfer library simplifies the process of handling Amazon S3 file transfers with Python. Whether you are managing large files, optimizing multi-threaded operations, or requiring customization, s3transfer provides all the tools you need to streamline your cloud storage operations.