Python 3.15 Is a Bigger Update Than I Expected

🧱 Build software that lasts. Join the Software Design Mastery program → arjan.codes/mastery. Python 3.15 brings some surprisingly useful changes, from lazy imports and a built-in immutable dictionary to a standard sentinel and a new way to flatten collections. In this video, I walk through the Python 3.15 features that are most likely to affect real projects, including `frozendict`, unpacking in comprehensions, the new sampling profiler, UTF-8 by default, typing improvements, and the latest progress on the JIT and free-threading. 🔥 GitHub Repository: git.arjan.codes/2026/py315 💬 Join my Discord server: discord.arjan.codes ⌨️ Keyboard I’m using: amzn.to/49YM97v 🔖 Chapters: 0:00 Intro 1:00 1. Lazy Imports 2:34 2. frozendict 4:15 3. A Built-In Sentinel 5:37 4. Unpacking Inside Comprehensions 6:22 5. Python Gets a Sampling Profiler 8:09 6. UTF-8 Is the Default 9:18 7. Typing for Extensible Data 10:34 8. The JIT and Free-Threading Direction 11:48 A Few Smaller Improvements 12:19 Final Thoughts #arjancodes #softwaredesign #python