A Study on the Pythonic Functional Constructs' Understandability

The use of functional constructs in programming languages such as Python has been advocated to help write more concise source code, improve parallelization, and reduce side effects. Nevertheless, their usage could lead to understandability issues. This paper reports the results of a controlled experiment conducted with 209 developers to assess the understandability of given Pythonic functional constructs---namely lambdas, comprehensions, and map/reduce/-filter functions---if compared to their procedural alternatives. To address the study's goal, we asked developers to modify code using functional constructs or not, to compare the understandability of different implementations, and to provide insights about when and where it is preferable to use such functional constructs. Results of the study indicate that code snippets with lambdas are more straightforward to modify than the procedural alternatives. However, this is not the case for comprehension. Regarding the perceived understandability, code snippets relying on procedural implementations are considered more readable than their functional alternatives. Last but not least, while functional constructs may help write compact code, improving maintainability and performance, they are considered hard to debug. Our results can lead to better education in using functional constructs, prioritizing quality assurance activities, and enhancing tool support for developers.