def upload_to_s3(s3key, filename, bucket, aws_key, aws_secret):
    conn = boto.connect_s3(aws_key, aws_secret)
    bucket = conn.get_bucket(bucket)
    # Get file info
    source_path = filename
    source_size = os.stat(source_path).st_size
    # Create a multipart upload request
    mp = bucket.initiate_multipart_upload(s3key)
    # Use a chunk size of 50 MiB
    chunk_size = 52428800
    chunk_count = int(math.ceil(source_size / chunk_size))
    # Send the file parts, using FileChunkIO to create a file-like object
    # that points to a certain byte range within the original file. We
    # set bytes to never exceed the original file size.
    for i in range(chunk_count + 1):
        print('Uploading file chunk: {0} of {1}'.format(i + 1, chunk_count + 1))
        offset = chunk_size * i
        bytes = min(chunk_size, source_size - offset)
        with FileChunkIO(source_path, 'r', offset=offset, bytes=bytes) as fp:
            mp.upload_part_from_file(fp, part_num=i + 1)
    # Finish the upload
    completed_upload = mp.complete_upload()
    return completed_upload