Why It Took 4 Years to Get a Lock Files Specification

Explore the complex journey behind Python's lock file specification in this keynote presentation from EuroPython 2025. Discover why it took four years to develop PEP 751, from its inception in January 2021 to its acceptance in March 2025, and understand the inherent challenges that make Python packaging uniquely difficult. Learn about the flexibility that has enabled over 600,000 projects on PyPI and made Python the glue language of the internet, while examining how this same flexibility creates complexity and prevents having "one tool to rule them all." Delve into the historical development of the lock file specification, understand what it provides to the Python ecosystem, and gain insights into the intricate world of Python packaging from Brett Cannon's expert perspective.