The empty operator returns an observable that completes immediately without sending any item:

The prototype of the empty operator is the following one:

Observable.empty(scheduler=None)

The empty operator can be used in the following way:

empty = Observable.empty()

empty.subscribe(
    on_next=lambda i: print("item: {}".format(i)),
    on_error=lambda e: print("error: {}".format(e)),
    on_completed=lambda: print("completed")
)

The empty operator is useful mainly for testing and for stubbing:

• During unit testing, it can be used to test components against empty observables as input. 
• When implementing a function step by step, for example when following a test-driven development process, an initial implementation can be done with empty observables.