The ReactiveX project is composed of several hundreds of operators, and the Python implementation contains about 140 of them. When writing ReactiveX code, especially in the early days, you should regularly refer to the operator's documentation. Do not hesitate to read through it to find the most adapted operator for your needs. This is a good way to discover operators that you may use later, and you may find an operator doing exactly what you want to implement.
Unfortunately, this documentation is often difficult to understand. A representative of this situation is the FlatMap (http://reactivex.io/documentation/operators/flatmap.html) operator description:
"Transform the items emitted by an Observable into Observables, then ...
