In case you use Django or Flask (or any Python framework) as your backend for a simple monolithic application where the front-end and backend are tightly coupled, jinja templates would make the job easier for you because you can take advantage of template variables passed on from the backend.
But as Luis pointed out, it would be better to follow a RESTful approach to build applications. You could use a micro-framework like Flask or Pyramid to serve the REST endpoints and use a front-end framework like React/Angular that interacts with the backend service. This way, if you have to build a whole new client (like a mobile or desktop app), it could still interact with your existing backend service. When you build a RESTful service, if the application might turn out huge/complex later, it would be good to follow API versioning right from the start. Here are some best practices on building RESTful services.