Python High Performance - Second Edition

Hot and cold observables

In the preceding section, we learned how to create an observable using the Observable.from_iterable method. RxPy provides many other tools to create more interesting event sources.

Observable.interval takes a time interval in milliseconds, period, and will create an observable that emits a value every time the period has passed. The following line of code can be used to define an observable, obs, that will emit a number, starting from zero, every second. We use the take operator to limit the timer to four events:

    obs = Observable.interval(1000)    obs.take(4).subscribe(print)    # Output:    # 0    # 1    # 2    # 3

A very important fact about Observable.interval is that the timer doesn't start until we subscribe. We can observe ...