For one week, Arm’s Cambridge headquarters became the heart of Python development. Contributors from around the world came together for the CPython Core Developer Sprint. It was the largest gathering in the project’s history, with 35 core developers and 13 invited guests collaborating in person.
Unlike a conference, the sprint is a working retreat. There are no spectators or formal keynotes, just space for deep technical debate, design, coding, and consensus-building. Hosting it at Arm’s Cambridge offices showed a shared commitment.
Python powers much of today’s software stack, from web and automation to machine learning, IoT, and cloud services. CPython is advancing with adding a JIT compiler, free-threading, and other modernization efforts. Making sure these innovations run well on Arm is part of making Python’s future truly platform-agnostic and robust.
The sprint offers a rare chance for real-time dialogue. Ideas can be sketched on whiteboards, trade-offs debated face-to-face, and tricky issues given momentum.
The week included technical presentations, collaborative work, and community events. Talks and presentations were grouped around key themes:
The program also included a Q&A with the Steering Council, where Barry Warsaw and Emily Morehouse joined remotely. It also featured a mentorship discussion led by Tania Allard on how to welcome and support new contributors.
Beyond presentations, the sprint fostered hands-on collaboration. Developers had advanced JIT planning, explored progress on free threading, and discussed improvements to documentation and translations. They also strengthened testing and CI across platforms, and refined governance and contributor onboarding processes.
Antonio Cuni highlighted real-world JIT pitfalls, which informed many of these discussions.
Finally, the sprint included community activities that helped balance the technical intensity with moments of connection. The Python Guild at Arm hosted an Ask Me Anything (AMA) session, giving local engineers the chance to interact with core developers.
A formal dinner at Jesus College reflected Cambridge traditions, while a punting trip on the River Cam offered a relaxed opportunity to connect outside of work.
The Python Software Foundation coordinated the event, making the sprint possible. We thank Phyllis Dobbs for managing the RSVP process and the travel grants that enabled many contributors to join us in Cambridge.
We also thank the people at Arm who made hosting the sprint possible. A special thank you goes to the Software Communities team, Arm’s financial sponsor. Without their support, the sprint would not have happened. In particular, thanks to Andrew Wafaa, who leads the team, and Charlie Dixon, who drove every detail. They covered everything from the venue, food, freebies, t-shirts, and the social event to handling all the last-minute requests. Events like this take a year to organize, and they have been supportive since day zero.
Thank you also to Ellie Stanford-Reed and Megan Knight. They began working with me a year ago and laid the foundations that made this sprint possible. Beyond the sprint, the Software Communities team has also sponsored EuroPython for three years. They continue to engage with and support other open-source communities.
We are grateful to Central Engineering Software management for backing the organization effort. Thanks also to the Facilities and Workplace teams for solving the challenging room layout and logistics. Also thank you to the People team for handling visa requests, and to IT for providing monitors, audio, video, and onsite support throughout the week.
Thanks also to Developer Marketing for sponsoring the event banner. To the Python Guild organizers for running the Guild AMA session on Friday, and to the onsite organizers at Arm who cleared space in their calendars to support the sprint throughout the week.
Finally, a huge thank you to all the attendees who travelled from across the world to spend a week in Cambridge. Some came from nearby in the UK and neighboring countries. Many others journeyed across Europe, several crossed the Atlantic, and a few took long haul and even ultra-long-haul flights of more than 10,000 km. That dedication and commitment to the Python community is what truly made this sprint special.
Organizing a sprint of this scale takes many hands. From sponsors to volunteers, organizers to attendees, everyone contributed in their own way. This sprint was a reminder that Python is more than a programming language. It is a community that works together, supports one another, and achieves more as a team than any individual could alone.
The sprint was widely regarded as a success. Attendees described it as productive, well organized, and an excellent community experience. Even so, some aspects could have been improved, and these are valuable lessons to take forward for future events.
Sessions such as the Steering Council Q&A, the mentorship discussion led by Tania Allard, and the lightning talks stood out as highlights. They reinforced the value of bringing the community together in person.
For Arm, this was more than providing a venue. It was an investment in strengthening one of the most influential open-source communities. Python’s reach is vast and ensuring its modern components run smoothly on Arm platforms helps the language stay inclusive and performant across architectures. Hosting the sprint gave Arm a way to give back, reinforce bonds with the core team, and invest in Python’s future.
Python is undergoing important technical transitions. Sprints like this accelerate evolution, resolve difficult challenges, and align the community. The concentration of expertise enabled focused, collaborative progress. The ripple effects of this sprint will shape code, discussion, and design decisions for months to come. We look forward to coming together again as a community.