You might want to build a GUI for your Machine Translation model to show to a client or to be able to translate sentences online. I have created a simple web interface for OpenNMT which depends on Python Flask and Flask-PageDown libraries. To be able to use the web interface, you need first to implement an OpenNMT Rest API Server as explained by Paul Tardy
at: Simple OpenNMT-py REST server.
You can find the code of the machine translation web interface at:
If you have questions, please let me know.