test.py
    =======
    import bottle
    
    @bottle.get('/')
    def index():
        return 'INDEX'
    
    # a new wsgi app
    hello = bottle.Bottle()
    
    @hello.get('/<name>')
    def greet(name):
        return 'Hello, ' + name
    
    bottle.app().mount('/hello', hello)

Test like this: python3 -m bottle --bind :8080 test

You should have 2 working routes, "/" and "/hello/<name>".