hello world with flask and redis using docker networking

The sample from Docker, a "hello world" with redis and flask, seems to build fine, but, as an exercise can it be broken into two components?

The redis service uses a public Redis image pulled from the Docker Hubregistry.

and

Compose pulls a Redis image, builds an image for your code, and startsthe services you defined. In this case, the code is statically copiedinto the image at build time.

What I have in mind is to use the default redis image as its own container, and then modify the flask app so that it connects to the redis image. This is reasonable?