A Python program using boto3 that does a multipart file upload to AWS S3 with file integrity checking. It approximates the instructions at https://aws.amazon.com/premiumsupport/knowledge-center/s3-multipart-upload-cli/ .
python s3_multipart_uploader.py s3bucketname filename.zip --storage-class=DEEP_ARCHIVE
There seems to be a problem on Amazon's side with checking the hash of the combined file (see here). This program should report a problem if any of the component uploads have hash failures, or if the completed file is the wrong size, so in practice the Amazon bug should not be a serious concern. However, for extra assurance it should be possible to run an appropriate hash function against the uploaded file with AWS Lambda and then check its results.
MIT (see included LICENSE file).