Yesterday’s video described the GIL in Python — its history, current usage, and future. It would seem that Python is destined to have a GIL in the foreseeable future. However, the PyPy alternative implementation of Python was designed to be a sandbox for new ideas, and for trying new ways of doing things in Python. One such idea is to bring software transactional memory (STM) to Python, simultaneously providing for concurrency and safety. How does STM work in PyPy? What does it change in the language? And why is this not already a part of Python? In this talk, Armin Rigo describes his work to integrate STM into PyPy, and what this means for Python developers now and in the future.