def upload_file(s3, bucketname, file_path):

        b = s3.get_bucket(bucketname)

        filename = os.path.basename(file_path)
        k = b.new_key(filename)

        mp = b.initiate_multipart_upload(filename)

        source_size = os.stat(file_path).st_size
        bytes_per_chunk = 5000*1024*1024
        chunks_count = int(math.ceil(source_size / float(bytes_per_chunk)))

        for i in range(chunks_count):
                offset = i * bytes_per_chunk
                remaining_bytes = source_size - offset
                bytes = min([bytes_per_chunk, remaining_bytes])
                part_num = i + 1

                print( "uploading part " + str(part_num) + " of " + str(chunks_count))

                with open(file_path, 'r') as fp:
                        fp.seek(offset)
                        mp.upload_part_from_file(fp=fp, part_num=part_num, size=bytes)

        if len(mp.get_all_parts()) == chunks_count:
                mp.complete_upload()
                print ("upload_file done")
        else:
                mp.cancel_upload()
                print ("upload_file failed")