Towards Effective Static Type-Error Detection for Python

In this experience paper, we design, implement, and evaluate a new static type-error detection tool for Python. To build a practical tool, we first collected and analyzed 68 real-world type errors gathered from 20 open-source projects. This empirical investigation revealed four key static-analysis features that are crucial for the effective detection of Python type errors in practice. Utilizing these insights, we present a tool called Pyinder, which can successfully detect 34 out of the 68 bugs, compared to existing type analysis tools that collectively detect only 16 bugs. We also discuss the remaining 34 bugs that Pyinder failed to detect, offering insights into future directions for Python type analysis tools. Lastly, we show that Pyinder can uncover previously unknown bugs in recent Python projects.