Hot Code Patching in CPython: Supporting Edit-and-Continue Debugging in CPython with Less Than 300 Lines of Code

Some language runtimes such as Java Hotspot or the virtual machine for Squeak/Smalltalk support edit-and-continue debugging, which allows developers to make changes to a program while it is running. This capability is especially useful for recovering from errors in a program. However, it is not supported by CPython, the reference interpreter for Python. In this paper, we demonstrate how edit-and-continue debugging can be integrated into CPython in just under 300 lines of code. We evaluate performance implications, demonstrate how this style of debugging improves the programming experience, and discuss limitations of our approach.