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core.py

by Pablo Galindo and Łukasz Langa

We talk about Python internals, because we work on Python internals. We joke about stuff, because we’re jokers. Episodes between 60 and 90 minutes in length. We’ve done more than a few so far and it doesn’t seem like we’ll be stopping any time soon!Hi Loren!

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Episodes

  1. Episode 30: Live from EuroPython, an Interview with Guido van Rossum

    This one is a short one. But it's also a big one. We'd invite you to listen to it, but you don't need to follow us. You don't need to follow anybody! You've got to think for yourselves! You're all individuals! ## Timestamps (00:00:00) INTRO (00:00:36) PART 1: GUIDO VAN ROSSUM (00:01:09) Monty...

  2. Episode 29: Is CPython developed with AI now?

    Let's talk about what it really means in practice that AI tools are used in the cpython GitHub repository now. First-hand opinions based on first-party experience. And some personal news! ## Timestamps (00:00:00) INTRO (00:00:58) PART 0: Developer Leaves Residence (00:09:15) Python's got more...

  3. Episode 28: 2025 In Review

    Let's take a breather from heavy content and take a look back at last year in this light but spicy episode! The good, the less good, and the disgusting. All that in barely an hour! ## Timestamps (00:00:00) INTRO (00:01:32) Pablo Galindo SPACE (00:06:20) PART 1: 2025 - the good, the uncertain, and...

  4. Episode 27: Calling Things, Part 1

    Inside of you there are two stacks. Actually, there’s three. The system-level call stack, the CPython call stack, and the interpreter’s evaluation stack. What is all that about? Today we’ll talk about how synchronous Python function calls work. Async stuff comes next time! ## Timestamps Here you…

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  5. Episode 26.2: CPython Sprint Week in Cambridge UK, Part 2

    More interviews from the core sprint! This time we have: Greg P. Smith, Thomas Wouters, Paul Ganssle, Pradyun Gedam, Carol Willing, Guido van Rossum, Brett Cannon, Erlend Aasland, Tal Einat, Lysandros Nikolaou, Yury Selivanov, and Diego Russo -- the organizer himself. ## Timestamps (00:00:00)…

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  6. Episode 26.1: CPython Sprint Week in Cambridge UK, Part 1

    What? What do you mean this two-and-a-half hour episode is PART 1? Well, there were fifty people at the sprint in September. We interviewed thirty of them. In Part 1 you can hear from 18 of them: Ken Jin, Alex Waygood, Russell Keith-Magee, Sam Gross, Steve Dower, Dino Viehland, Petr Viktorin…

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  7. Episode 25: A Python That Never Was

    What if some rejected PEPs were actually accepted? How would Python look today? Let's go through 10 PEPs from the past and imagine an alternative future for the language! ## Timestamps (00:00:00) INTRO (00:01:00) PART 1: What if rejected PEPs were accepted? (00:02:15) PEP 638: Syntactic Macros...

  8. The Megahertz

    Python 3.14? That's old news. Let's talk about the first big feature of Python 3.15 -- a built-in sampling profiler for Linux, macOS, and Windows. We also cover improvements in perf support, discuss memory.python.org, and as usual, recent changes in the codebase. ## Timestamps (00:00:00) INTRO...

  9. PyCon US 2025 Recap

    We’ve been gone a while. Here’s our excuse for being silent for a month: PyCon, PyCon, something something security. Come listen to how the conference looked like from our perspective! And whatever you do, DO NOT upgrade to Python 3.13.4. ## Timestamps (00:00:00) INTRO (00:01:06) PART 1: LANGUAGE...

  10. Beta Frenzy

    Python 3.14 Beta 1 is coming! And that means we reach feature freeze. BUT QUICK, there’s still time to squeeze in one last thing! ## Timestamps (00:00:00) INTRO (00:01:58) PART 1: Template strings (00:07:10) PART 2: Asyncio Introspection (00:29:07) PART 3: Syntax highlighting (00:43:00) PART 4:...

  11. Episode 21: A Garbage Episode

    We talked about this episode for months now, and it's finally here. Garbage collection in its full glory. Classic and free-threaded. Generational and single-pass. With eager and delayed untracking. We cover it all! Explicitly. ## Timestamps (00:00:00) THE FUCKING INTRO (00:02:03) PART 0: SPORTS...

  12. Episode 20: Remote Code Execution By Design

    In this episode, Pablo's avoiding the topic of garbage collection by talking about his latest PEP, which allows unprecedented interaction with a running Python process. We also resolve the bet about reference counting semantics, mention some notable changes in Python since the last episode, and...

  13. Episode 19: Async hacks, unicorns and velociraptors

    In this asynchronous episode we're interviewing a fellow core developer Yury Selivanov to talk about asyncio's past and future, composable design, immutability, and databases you'd actually like using. We also broke the 2-hour episode barrier! ## Timestamps (00:00:00) INTRO (00:01:33) PART 1:...

  14. Episode 18: Reference Counting

    After we talked about memory allocation in Python back in Episode 16, we're ready to complain, uh, explain reference counting. Or at least throw a bunch of reference counting facts at you. Plus a big assortment of recent Python changes. You ready? ## Timestamps (00:00:00) INTRO (00:04:17) PART 0:...

  15. Episode 17: Argparse, JIT, and balloons with Savannah Ostrowski

    Meet our newest member of the core developer team, Savannah! Currently at Snowflake, she also worked with development tools at Docker and Microsoft, but also flew drones over forests. In terms of CPython, Savannah works on argparse and the JIT, but that's not her last word. # Timestamps…

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  16. Episode 16: Memory Allocation

    How does Python handle memory? Why does it need to perform custom forms of memory allocation? We talk about all that in this episode. We don't talk about Easter eggs, and we never mention Brandt by name, as promised last time! ## Timestamps (00:00:00) INTRO (00:00:22) PART 0: SPORTS NEWS…

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  17. Episode 15: Core sprint at Meta

    Over 40 core developers spent a week in Bellevue WA putting finishing touches on Python 3.13, planning, prototyping, and implementing features for Python 3.14. We talked to half of them. We laughed, we cried. We were happy watching graphs go up, and sad watching them go down. It was intense.…

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  18. Episode 14: Integration Events

    We’ve been gone all Summer, visiting two European conferences in the mean time. In this episode we’re talking about them both, talks we liked, as well as our own talks at those events. In a rare turn of events, this one was recorded in person at Łukasz’s home studio in Poznań! ## Outline…

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  19. Episode 13: A Legit Episode

    In this lucky episode we're interviewing fellow core developer Brandt Bucher to talk about Justin, Swedish warships, and the n-body benchmark. We're also breaking the duration record with this one. We promise we'll get faster in future releases! ## Outline (00:00:00) INTRO (00:01:43) PART 1…

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  20. Episode 12: WTF Python

    You think you know Python? We thought so, too. Join us for an episode of surprises. You might know some of those, but you sure don't know all of them. ## Outline (00:00:00) INTRO (00:02:22) Integer interning with a twist (00:10:58) Return in finally (00:15:32) all([[]]) (00:20:06) Lists…

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  21. Episode 11: Live from PyCon 2024

    Who says we can't do short episodes? Well, it was a challenge! But with the help of some gentle conference schedule pressure, here's our first sub-hour episode. We're discussing the language summit, answering audience questions, and behaving like serious professionals, as usual. ## Outline...

  22. Episode 10: The Interactive REPL

    Oof, no episode in April, huh? Yeah, we're getting close to Python 3.13 beta 1. PyCon US is also coming up real soon. Let's use this opportunity then to talk about a feature we're teaming up on: a better interactive interpreter! ## Outline (00:00:00) INTRO (00:01:53) PART 1: History of Terminals...

  23. Episode 9: Py Day with Emily Morehouse-Valcarcel

    Let's talk about the Steering Council, running a small consultancy business, the Walrus, and pet peeves with our special guest today! ## Outline (00:00:00) INTRO (00:00:56) PART 1: Emily Morehouse (00:02:15) Running a small consultancy business (00:04:39) What features of JS do you miss in…

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  24. Episode 8: The New Parser

    The suspense was killing us! OK, the old parser was then... but what about NOW? We're finally answering this question... in more detail than you dared to ask for. PEG, memoization, funky secrets, and how a certain auto-formatter self-inflicted an existential crisis on itself. It's all there, told...

  25. Episode 7: The Old Parser

    Context-free grammars, non-deterministic finite automatons, left-to-right leftmost derivations... what even is all that?! Today we're talking about how Python parses your source code. We start gently with how this worked in the past. Come listen to Łukasz's high-level explanations and Pedantic...

  26. Episode 6 - An Exceptional Episode

    Happy New Year! In this episode we're talking about exceptions, how they work, and how they evolved. Expect the unexpected. # Timestamps (00:00:00) INTRO (00:01:43) How does a 'try' block work? (00:04:00) How many 'try' blocks can you fit on a bus? (00:05:56) How does Python store the current...

  27. Episode 5 - Cinder with Carl Meyer

    This time we're hosting a special guest: Carl Meyer from Meta. What is Cinder, how does it work, and how does it intersect with the future of Python 3? Find out in today's episode. 100% serious stuff! # Timestamps (00:00:00) INTRO (00:00:53) Carl Meyer's war story (00:02:27) CINDER (00:03:22)...

  28. Episode 4 - Frame Evaluation

    What makes Python an interpreter? Today we're talking about ceval.c, the wonders of frame evaluation, and how it changed over the years. # Timestamps (00:00:00) INTRO (00:00:59) BACK TO PYTHON 2.6 (00:02:53) Stack virtual machine (00:04:41) First encounter with opcodes (00:08:06) What even is…

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  29. Episode 3 - Imports, frozen modules, Python news

    What happens when you type “import abc”? Why does it say the module is frozen? What significant changes landed in Python in the past two weeks? And why does the “PR of the Week” jingle go so hard? Find out in this week’s episode! # Timestamps (00:00:00) INTRO (00:01:12) IMPORTS (00:02:21) Here be...

  30. Episode 2 - PEP 703: Removing the GIL

    We've read the PEP on making the Global Interpreter Lock optional so you don't have to. Timestamps (00:00:00) Intro (00:00:50) CURRENT STATE OF THINGS (00:00:58) Reference counting (00:01:35) Garbage collection (00:02:33) What is the Global Interpreter Lock? (00:03:57) The GIL and threading...

  31. Episode 1 - Core Sprint in Brno & Python 3.13.0 alpha 1

    In this first episode Pablo and Łukasz talk about what happened in at the 2023 Cpython Core Developer sprint. Join us and learn from our ramblings about a possible new CPython new JIT compiler, how we are making the REPL easier, what in the world is a memory hive, and how we are trying to make a...

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ABOUT THIS SHOW

We talk about Python internals, because we work on Python internals. We joke about stuff, because we’re jokers. Episodes between 60 and 90 minutes in length. We’ve done more than a few so far and it doesn’t seem like we’ll be stopping any time soon!Hi Loren!

HOSTED BY

Pablo Galindo and Łukasz Langa

CATEGORIES

Frequently Asked Questions

How many episodes does core.py have?

core.py currently has 31 episodes available on PodParley. New episodes are automatically indexed when they're published to the podcast feed.

What is core.py about?

We talk about Python internals, because we work on Python internals. We joke about stuff, because we’re jokers. Episodes between 60 and 90 minutes in length. We’ve done more than a few so far and it doesn’t seem like we’ll be stopping any time soon!Hi Loren!

How often does core.py release new episodes?

core.py has 31 episodes. Check the episode list to see recent publication dates and frequency.

Where can I listen to core.py?

You can listen to core.py on PodParley by clicking any episode. We provide an embedded audio player for direct listening, and you can also subscribe via your preferred podcast app using the RSS feed.

Who hosts core.py?

core.py is created and hosted by Pablo Galindo and Łukasz Langa.
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