How Do Python Framework APIs Evolve? An Exploratory Study

Python is a popular dynamic programming language. In recent years, many frameworks implemented in Python have been widely used for data science and web development. Similar to frameworks in other languages, the APIs provided by Python frameworks often evolve, which would inevitably induce compatibility issues in client applications. While existing work has studied the evolution of frameworks in static programming languages such as Java, little is known on how Python framework APIs evolve and the characteristics of the compatibility issues induced by such evolution. To bridge this gap, we take a first look at the evolution of Python framework APIs and the resulting compatibility issues in client applications. We analyzed 288 releases of six popular Python frameworks from three different domains and 5,538 open-source projects built on these frameworks. We investigated the evolution patterns of Python framework APIs and found that they largely differ from those of Java framework APIs. We also investigated the compatibility issues in client applications and identified common strategies that developers adopt to fix these issues. Based on the empirical findings, we designed and implemented a tool, PC, to automatically detect compatibility issues caused by misusing evolved framework APIs in Python applications. Experiments on 10 real-world projects show that our tool can effectively detect compatibility issues of developers' concern.