This chapter detailed the different ways to create observables, from either existing objects or custom code logic. The factory operators that we documented are the ones that allow us to start any operator chain in ReactiveX. Of this list of operators, from_, create, and just are probably used the most frequently.

Understanding the difference between cold and hot observables is very important when developing a ReactiveX application. If this notion is not clear to you, you will not understand why some values are received several times on a cold observable or why some values are never received on a hot observable.

The previous chapters already contained examples of observable subscriptions. Now the different ways to subscribe to an observable, as well as how to handle errors, should be clear.

Finally, the last part of this chapter presented some tools that allow us to bridge observables and futures. These operators are useful in some cases, but it is also possible to make AsyncIO and ReactiveX cohabit via other code logic if they do not match the logic of an application.

The next chapter will be dedicated to concurrency and parallelism. RxPY has provided many ways to handle concurrency. Next, we will study how to use the AsyncIO event loop with RxPY. However, RxPY also allows us to do parallelism since Python has some limitations in this field.