Functional pipelining is a cornerstone in reactive programming. Operators carry out operations on streams or observables that produce other streams or final results. In this chapter, we discuss different types of operators and illustrate their usage and patterns to make functional lineages. Afterwards, we implement them in Python and in PyFunctional, a python minimalistic library for functional pipelines. Implementing lazy evaluation and optimising execution strategies are two important themes that affect performance. Hence, drawbacks of functional pipelining and how to overcome them when possible will be discussed as well.