Python - upload file to S3 using boto3

Get S3 Session

import boto3

def _get_s3_session():
    envvars = subprocess.check_output(
        ['aws-vault', 'exec', 'your-aws-role', '--', 'env'])

    aws_access_key_id = ''
    aws_secret_access_key = ''
    aws_session_token = ''
    for envline in envvars.split(b'\n'):
        line = envline.decode('utf8')
        eqpos = line.find('=')
        if eqpos < 4:
            continue
        k = line[0:eqpos]
        v = line[eqpos + 1:]
        if k == 'AWS_ACCESS_KEY_ID':
            aws_access_key_id = v
        if k == 'AWS_SECRET_ACCESS_KEY':
            aws_secret_access_key = v
        if k == 'AWS_SESSION_TOKEN':
            aws_session_token = v

    session = boto3.Session(aws_access_key_id, aws_secret_access_key, aws_session_token)
    return session

Upload files to S3

class ProgressPercentage(object):
    def __init__(self, filename, size=None, prefix_str=''):
        self._filename = filename
        if size is None:
            self._size = float(os.path.getsize(filename))
        else:
            self._size = size
        self._prefix_str = prefix_str
        self._seen_so_far = 0
        self._lock = threading.Lock()

    def __call__(self, bytes_amount):
        # To simplify we'll assume this is hooked up
        # to a single filename.
        with self._lock:
            self._seen_so_far += bytes_amount
            percentage = (self._seen_so_far / self._size) * 100
            sys.stdout.write(
                "\r%s %s / %s  (%.2f%%)" % (
                    self._prefix_str,
                    self._seen_so_far,
                    self._size,
                    percentage))
            sys.stdout.flush()

def _upload_to_s3(self, **kwargs):
    start = time.time()

    self._object_name = kwargs['object_name']
    self._file_path = kwargs['path']
    self._bucket_name = kwargs['bucket_name']

    # If S3 object_name was not specified, use file_name
    if self._object_name is None:
        self._object_name = ntpath.basename(self._file_path )
    # Upload the file
    session = _get_s3_session()
    s3_client = session.client("s3")

    try:
        # Perform the transfer
        s3_client.upload_file(
            self._file_path,
            self._bucket_name,
            self._object_name,
            Callback=ProgressPercentage(
                self._file_path,
                prefix_str='Uploading file {:} -> {:}.{:}: '.format(
                    os.path.dirname(self._file_path), self._bucket_name, self._object_name)),
        )