Thursday, July 21, 2022

Distinguished Service Award Granted to Naomi Ceder

Naomi Ceder, a longtime Python activist and organizer has been recognized with the PSF’s Distinguished Service Award. Naomi served on the PSF Board from 2015-2020, and as Chair from 2017-2020, supported the search for a new Executive Director last year and keynoted the most recent PyCon US in Salt Lake City.

The PSF’s Distinguished Service Award (DSA) is granted to individuals who make sustained exemplary contributions to the Python community. Each award is voted on by the PSF Board and they are looking for people whose impact has positively and significantly shaped the Python world. Naomi’s work with the Python community very much exemplifies the ethos of “build the community you want to see.” She seems to particularly enjoy taking on the hardest parts, getting a new initiative started and figuring out how to take an idea from the drawing board to a regular activity that we can’t imagine leaving out.

After receiving the award Naomi shared, "I'm so grateful for the recognition, and even more grateful for all of the support that our community has given me over the years. I'm excited to see a new generation of Python volunteers continue the work to make our community and the PSF more global and inclusive, and I'm looking forward to working with smaller communities as they grow and develop."

Over the years Naomi has taken on many leadership roles to make PyCon US successful and welcoming. She served as Chair of the Hatchery Program and she helped found PyCon Charlas, our Spanish language track. At different points in time, she’s also been the Co-chair of Sprints, an Organizer of the PyCon Education Summit and Chair for poster sessions at PyCon US. She also co-founded Trans*Code, an on-going series of hackdays (mostly) in the UK, which aims to build community and foster tech education and skills for transgender and non-binary folks. PyCon US and the global Python community would not look like it does without her tireless, largely behind the scenes work. Her deep thoughtfulness coupled with her energy is an immeasurable gift to the Python community. 

Curious about previous recipients of the DSA or wondering how to nominate someone? We got you.

Wednesday, July 06, 2022

Announcing Python Software Foundation Fellow Members for Q2 2022! 🎉

The PSF is pleased to announce its second batch of PSF Fellows for 2022! Let us welcome the new PSF Fellows for Q2! The following people continue to do amazing things for the Python community:

Archana Vaidheeswaran
Carlton Gibson
Jürgen Gmach
Matteo Benci
Matthew Lagoe
Paul McGuire
Reshama Shaikh
Seth Michael Larson
Thomas A Caswell

Thank you for your continued contributions. We have added you to our Fellow roster online.

The above members help support the Python ecosystem by being phenomenal leaders, sustaining the growth of the Python scientific community, maintaining virtual Python communities, maintaining Python libraries, creating educational material, organizing Python events and conferences, starting Python communities in local regions, and overall being great mentors in our community. Each of them continues to help make Python more accessible around the world. To learn more about the new Fellow members, check out their links above.

Let's continue recognizing Pythonistas all over the world for their impact on our community. The criteria for Fellow members is available online: If you would like to nominate someone to be a PSF Fellow, please send a description of their Python accomplishments and their email address to psf-fellow at We are accepting nominations for quarter 3 through August 20, 2022.

Are you a PSF Fellow and want to help the Work Group review nominations? Contact us at psf-fellow at

Friday, July 01, 2022

Board Election Results for 2022!

Congratulations to everyone who won a seat on the PSF Board! We’re so excited to work with you. New and returning Board Directors will start their three year terms this month at the next PSF board meeting. Thanks to everyone else who ran this year and added their voice to the conversation about the future of the Python community. It was a tough race with many amazing candidates. 

  • Kushal Das
  • Jannis Leidel
  • Dawn Wages
  • Simon Willison

Thanks to everyone who voted and helped us spread the word! We really appreciate that so many of you took the time to participate in our elections this year. By the numbers, we sent ballots to 1,459 voting PSF members who then chose among 26 nominees. By the end 578 votes were cast, well over the one third required for quorum.

While the board elections are over, there are lots of other ways to get involved with the Python community. Here are a few things you can get started with or you could consider serving with one of our working groups. If you want to start participating on the technical side of things, you might want to check out our forum. Next year’s board elections will happen at approximately the same time in 2023. If you want to make sure you are notified via email, join the psf-vote mailing list.

Sunday, June 19, 2022

The PSF Board Election is Open!

It’s time to cast your vote! Voting takes place from Monday, June 20 AoE, through Thursday, June 30, 2022 AoE. Check here to see how much time you have left to vote. If you are a voting member of the PSF, you will get an email from “Helios Voting Bot <>” with your ballot, subject line will read “Vote: Python Software Foundation Board of Directors Election 2022”. If you haven’t seen your ballot by Tuesday, please 1) check your spam folder for a message from “” and if you don’t see anything 2) get in touch by emailing so we can make sure we have the most up to date email for you.

This might be the largest number of nominees we’ve ever had! Make sure you schedule some time to look at all their statements. We’re overwhelmed by how many of you are willing to contribute to the Python community by serving on the PSF board.

Who can vote? You need to be a Contributing, Managing, Supporting, or Fellow member as of June 15, 2022 to vote in this election. Read more about our membership types here or if you have questions about your membership status please email

Thursday, June 09, 2022

The PSF's 2021 Annual Report

2021 was a challenging and exciting year for the PSF. We’ve done our best to capture some of the key numbers, details, and context in our latest annual report. Some highlights of what you’ll find in the annual report include: 

  • Letter from our outgoing Board Chair Lorena Mesa
  • Personal reflection on the PSF’s 20th anniversary from our outgoing interim general manager and longtime community member Thomas Wouters
  • Note from our new Executive Director Deb Nicholson
  • Account by Łukasz Langa on what he’s accomplished and learned in his first year as the inaugural PSF Developer in Residence
  • PyCon US 2021 by the numbers
  • Where we sent grant funding in 2021
  • Summary of our 2021 financials
  • Great photos plus testimonials from some of the small number of live events the PSF supported in 2021, generously shared by these groups who are doing great work for the Python community around the world:
  • Sponsors who generously supported our work and the Python ecosystem in 2021

We’d love for you to take a look, and if you do, let us know what you think! You can comment here, tweet at us, or share your thoughts on

Wednesday, June 08, 2022

PyCon US: Successful Return to In-Person in 2022

We held our first in-person event since 2019 in Salt Lake City last month and it was well-attended, celebratory, and safe. We had 1,753 in-person attendees and 669 online attendees. Of the in-person attendees, 1,153 were attending their first PyCon US ever – we hope they’ll all be back! In-person attendees were masked and we took care to add extra space to the expo hall, the dining areas, the session rooms and the job fair. For many community members, this was their first in-person conference or community event of any type in almost 3 years. There were a LOT of hugs and some very enthusiastic -- elbow bumps. 

You can take a look at PyCon 2022 by the numbers here. 


Having joined the PSF as Executive Director just a few weeks before the event, this was a great opportunity to meet the community, including long-time volunteers, current and former board members, and hard-working local Python organizers from all over the world. It was also my first opportunity to meet the amazing PSF staff in person. Did you know that the PSF facilitates PyCon US with just 8 staff members? Their dedication to providing a space that is welcoming and fun, while also being safe and respectful, knows no bounds. The community is always first at PyCon US. 


We had lots of great talks and convened summits focused on Maintainers, Typing, Education, Packaging and the development of the Python Language. We also hosted Mentored Sprints for Diverse Beginners, the PyLadies Auction, four Lightning Talk Sessions, and two days of Sprints. We hit a few snags with a new AV team this year, but now most of the videos are up on our YouTube channel


This year’s event was a little more cautious, but it was really nice to see people. We’re actively looking for ways to better engage our online attendees next year and would welcome your ideas. Thanks to our many, many volunteers, especially three-time PyCon US Chair Emily Morehouse! Thank you also to our wonderful sponsors, many of whom not only help us put on PyCon US but also support the Python Programming Language throughout the year!!


Mark your calendar for PyCon US 2023 from April 19th to April 27th, 2023 both in Salt Lake City or online. If you are interested in talking about sponsorship opportunities for 2023, please drop us a line. And we are always looking for more volunteers, so if you’d like to be part of a future event as a volunteer, just let us know.

Tuesday, June 07, 2022

Welcome Chloe Gerhardson to the PSF staff!

With great anticipation and excitement we are happy to announce that Chloe Gerhardson (she/her) has joined the Python Software Foundation (PSF) as of Monday May 23, 2022. Chloe joins the team as Infrastructure Engineer, led by PSF Director of Infrastructure Ee Durbin.

Chloe Gerhardson - PSF Infrastructure Engineer

As a recent graduate of Springfield Technical Community College’s associates program in Computer Programming, Chloe will be growing into a role that supports the wide gamut of software technologies that facilitate the technical aspects of our community.

In time Chloe will share in all responsibilities of the Infrastructure Team and help the PSF move its infrastructure commitment to the community from a reactive and maintenance stance towards progress on new and expanded services to fulfill our mission.

In her own words…

I am thrilled and grateful to be brought along in the journey of growing and maintaining the PSF’s infrastructure, and I look forward to working with the PSF’s incredible staff members, as well as our wonderful community members at large.

Although excitement abounds for the learning, growing, and doing that this role requires Chloe also stays busy as a committed, registered, and active Registered Yoga Teacher in her community, skateboarder, dog lover, traveler, and aficionado of live music.

Please join us in welcoming Chloe!

Friday, June 03, 2022

Python Developers Survey 2021: Python is everywhere

We are excited to announce the results of the fifth official annual Python Developers Survey. This work is done each year as a collaborative effort between the Python Software Foundation and JetBrains. Late last year, more than 23,000 Python developers and enthusiasts from almost 200 countries/regions participated in the survey to reveal the current state of the language and the ecosystem around it.

Python is being used by the vast majority (84%) of survey respondents as their primary language and by many others as just one more tool in their box. Interestingly, only 29% of the Python developers involved in data analysis and machine learning consider themselves to be Data Scientists. And like past years, many use Python in conjunction with other popular development and data tools like SQL, Jupyter Notebook, Virtualenv, Docker or with the most popular web development technologies including Django, Javascript and HTML. 

Results of the 2021 Python Developers Survey

This is also the first time we have packaging information in the survey. It was interesting to see the wide range of tools that Python users are employing for their packaging tasks. The PSF is currently focusing on improving the packaging ecosystem and building a roadmap for the future of packaging. We hope you will continue sharing your opinions with us on this part of your work so that we can continue improving. 

Here's a link to the raw data, if you want to go deeper. 

If you do look at the raw data and discover things you think the community would be interested in, we hope you’ll let us know. Please share your thoughts on Twitter or other social media, mentioning @jetbrains and @ThePSF with the #pythondevsurvey hashtag. We are also open to any suggestions and feedback related to this survey which could help us run an even better one next time. You are also encouraged to open issues here or join the conversation on our forum.

Wednesday, June 01, 2022

PSF Board Election Dates for 2022

Board elections are a chance for the community to help us find the next batch of folks to help us steer the PSF. This year there are 4 seats open on the PSF board. You can see who is on the board currently here. (Kushal, Jannis, Lorena and Marlene are at the end of their current terms.) Nominations for new board members opens today!


  • Nominations are open, Wednesday, June 1st 12:00 PM Eastern
  • Board Director Nomination cut-off: Wednesday, June 15, 2022 AoE
  • Voter application cut-off date: Wednesday, June 15, 2022 AoE
  • Announce candidates: Thursday, June 16th
  • Voting start date: Monday, June 20, 2022 AoE
  • Voting end date: Friday, June 30, 2022 AoE

Nominations should be made through this form (Note: you will need to sign into or create your user account first). You can nominate yourself or someone else, but no one will be forced to run, so you may want to consider reaching out to someone before nominating them.  

You need to be a contributing, managing, supporting, or fellow member by June 15th to vote in this election. Learn more about membership here or if you have questions about membership or nominations please email

You are welcome to join the discussion about the PSF Board election on our forum or come find us in Slack.

Thursday, May 26, 2022

PyCon JP Association Awarded the PSF Community Service Award for Q4 2021

The PyCon JP Association team from left to right. Takayuki, Shunsuke, Jonas, Manabu, Takanori

The PyCon JP Association team was awarded the 2021 Q4 Community Service Award.

RESOLVED, that the Python Software Foundation award the 2021 Q4 Community Service Award to the following members of the PyCon JP Association for their work in organizing local and regional PyCons, the work of monitoring our trademarks, and in particular organizing the "PyCon JP Charity Talks" raising more than $25,000 USD in funds for the PSF: Manabu Terada, Takanori Suzuki, Takayuki Shimizukawa, Shunsuke Yoshida, Jonas Obrist.

We interviewed Jonas Obrist on behalf of the PyCon JP Association to learn more about their inspiration, their work with the Python community, and supporting the Python Software Foundation - PSF. Débora Azevedo also contributed to this article, by sharing more light on the PyCon JP Association's efforts and commitment to the Python community.

Jonas Obrist Speaks on the motivation behind the PyCon JP Association

What inspired the PyCon JP Association team into raising funds to support the PSF?

We were inspired to raise funds after reading an announcement by the PSF about the impact of the pandemic on the foundation and PyCon US. We could of course empathize with the struggle given that we have a similar situation, even if on a much smaller scale.

We tried to think of a good way to help and either Manabu or Takanori came up with the idea to host online events with presentations by members of the community with all proceeds going to the PSF. We held two such events so far with over a hundred attendees and even managed to gather some companies and individuals as sponsors. 

Thanks to the online nature, costs were kept very low and we were able to make a sizeable donation to the PSF, hopefully softening the financial blow of the pandemic a bit.

How do you think other Python communities can support the PSF?

I think other communities have various ways to support the PSF depending on each community's situation.

We have the fortune to be well established with great support from the wider community and especially local companies, so we were able to make a direct financial contribution

Not all communities are this fortunate, but I think there are still other ways to contribute.

One such way is simply to boost awareness of the Python programming language in the local developer community. ideally, this would eventually lead to companies adopting Python more widely, which in turn could lead to direct support to the PSF, either via direct donations or support of PyCon US by these companies.

Boosting local communities also leads to more Python developers in general, leading to a broader pool of people who could support the PSF in various ways.

The most important thing is for each community to think about what they can do, even if it is just a small thing, given that we owe so much to the PSF.

Débora Azevedo speaks about the impact and significance of the PyCon JP Association

One of the things I am most excited about is seeing the PyCon JP Association team receiving this CSA and realizing that the work being done outside the US-Europe countries is acknowledged.

PyCon JP association has risen to the financial challenge that the PSF went through due to the pandemic and has organized PyCon JP Charity Talks. Aiming to increase awareness within the industry about the importance of the PSF is so meaningful. The charity talks were initiatives by the PyCon JP association, and it was a significant effort on their part. Their work is such an outstanding work that shouldn't be overlooked.

As part of the wider Python community, it warms my heart to see that there are many amazing people worldwide working so we can have a more sustainable Python community.

Seeing local communities contributing to the global community, especially regarding this financial aspect, shows that the community feels the need to have different types of work done and understands the importance and impact of each one of them.

And, as part of the Diversity and Inclusion workgroup and understanding the impact of seeing people from non-US-based communities being acknowledged for doing the work, it feels like we are being heard.

The PyCon JP association's community work is outstanding and I am so grateful to them and for being in a community that values each contribution to its development and growth.

The Python Software Foundation congratulates and celebrates the PyCon JP association team -  Manabu TeradaTakanori SuzukiTakayuki ShimizukawaShunsuke YoshidaJonas Obrist.

You can learn more about making a donation to the PSF here.

Wednesday, May 11, 2022

The 2022 Python Language Summit: Lightning talks

These were a series of short talks, each lasting around five minutes.

Read the rest of the 2022 Python Language Summit coverage here.

Lazy imports, with Carl Meyer

Carl Meyer, an engineer at Instagram, presented on a proposal that has since blossomed into PEP 690: lazy imports, a feature that has already been implemented in Cinder, Instagram’s performance-optimised fork of CPython 3.8.

What’s a lazy import? Meyer explained that the core difference with lazy imports is that the import does not happen until the imported object is referenced.


In the following Python module,, with lazy imports activated, the module eggs would never in fact be imported since eggs is never referenced after the import:

# import sys import eggs def main(): print("Doing some spammy things.") sys.exit(0) if __name__ == "__main__": main()

And in this Python module,, with lazy imports activated, the function bacon_function is imported – but only right at the end of the script, after we’ve completed a for-loop that’s taken a very long time to finish:

import sys
import time
from bacon import bacon_function def main(): for _ in range(1_000_000_000): print('Doing hammy things') time.sleep(1) bacon_function()
sys.exit(0) if __name__ == "__main__": main()

Meyer revealed that the Instagram team’s work on lazy imports had resulted in startup time improvements of up to 70%, memory usage improvements of up to 40%, and the elimination of almost all import cycles within their code base. (This last point will be music to the ears of anybody who has worked on a Python project larger than a few modules.)


Meyer also laid out a number of costs to having lazy imports. Lazy imports create the risk that ImportError (or any other error resulting from an unsuccessful import) could potentially be raised… anywhere. Import side effects could also become “even less predictable than they already weren’t”.

Lastly, Meyer noted, “If you’re not careful, your code might implicitly start to require it”. In other words, you might unexpectedly reach a stage where – because your code has been using lazy imports – it now no longer runs without the feature enabled, because your code base has become a huge, tangled mess of cyclic imports.

Where next for lazy imports?

Python users who have opinions either for or against the proposal are encouraged to join the discussion on

Python-Dev versus Discourse, with Thomas Wouters

This was less of a talk, and more of an announcement.

Historically, if somebody wanted to make a significant change to CPython, they were required to post on the python-dev mailing list. The Steering Council now views the alternative venue for discussion,, to be a superior forum in many respects.

Thomas Wouters, Core Developer and Steering Council member, said that the Steering Council was planning on loosening the requirements, stated in several places, that emails had to be sent to python-dev in order to make certain changes. Instead, they were hoping that would become the authoritative discussion forum in the years to come.

Asks from Pyston, with Kevin Modzelewski

Kevin Modzelewski, core developer of the Pyston project, gave a short presentation on ways forward for CPython optimisations. Pyston is a performance-oriented fork of CPython 3.8.12.

Modzelewski argued that CPython needed better benchmarks; the existing benchmarks on pyperformance were “not great”. Modzelewski also warned that his “unsubstantiated hunch” was that the Faster CPython team had already accomplished “greater than one-half” of the optimisations that could be achieved within the current constraints. Modzelewski encouraged the attendees to consider future optimisations that might cause backwards-incompatible behaviour changes.

Core Development and the PSF, with Thomas Wouters

This was another short announcement from Thomas Wouters on behalf of the Steering Council. After sponsorship from Google providing funding for the first ever CPython Developer-In-Residence (Łukasz Langa), Meta has provided sponsorship for a second year. The Steering Council also now has sufficient funds to hire a second Developer-In-Residence – and attendees were notified that they were open to the idea of hiring somebody who was not currently a core developer.

“Forward classes”, with Larry Hastings

Larry Hastings, CPython core developer, gave a brief presentation on a proposal he had sent round to the python-dev mailing list in recent days: a “forward class” declaration that would avoid all issues with two competing typing PEPs: PEP 563 and PEP 649. In brief, the proposed syntax would look something like this:

forward class X() continue class X: # class body goes here def __init__(self, key): self.key = key

In theory, according to Hastings, this syntax could avoid issues around runtime evaluation of annotations that have plagued PEP 563, while also circumventing many of the edge cases that unexpectedly fail in a world where PEP 649 is implemented.

The idea was in its early stages, and reaction to the proposal was mixed. The next day, at the Typing Summit, there was more enthusiasm voiced for a plan laid out by Carl Meyer for a tweaked version of Hastings’s earlier attempt at solving this problem: PEP 649.

Better fields access, with Samuel Colvin

Samuel Colvin, maintainer of the Pydantic library, gave a short presentation on a proposal (recently discussed on to reduce name clashes between field names in a subclass, and method names in a base class.

The problem is simple. Suppose you’re a maintainer of a library, whatever_library. You release Version 1 of your library, and one user start to use your library to make classes like the following:

from whatever_library import BaseModel class Farmer(BaseModel): name: str fields: list[str]

Both the user and the maintainer are happy, until the maintainer releases Version 2 of the library. Version 2 adds a method, .fields() to BaseModel, which will print out all the field names of a subclass. But this creates a name clash with your user’s existing code, wich has fields as the name of an instance attribute rather than a method.

Colvin briefly sketched out an idea for a new way of looking up names that would make it unambiguous whether the name being accessed was a method or attribute.

class Farmer(BaseModel): $name: str $fields: list[str] farmer = Farmer(name='Jones', fields=['meadow', 'highlands']) print(farmer.$fields) # -> ['meadow', 'highlands'] print(farmer.fields()) # -> ['name', 'fields']

The 2022 Python Language Summit: Achieving immortality

What does it mean to achieve immortality? At the 2022 Python Language Summit, Eddie Elizondo, an engineer at Instagram, and Eric Snow, CPython core developer, set out to explain just that.

Only for Python objects, though. Not for humans. That will have to be another PEP.

Objects in Python, as they currently stand

In Python, as is well known, everything is an object. This means that if you want to calculate even a simple sum, such as 194 + 3.14, the Python interpreter must create two objects: one object of type int representing the number 194, and another object of type float representing the number 3.14.

All objects in Python maintain a reference count: a running total of the number of active references to that object that currently exist in the program. If the reference count of an object drops to 0, the object is eventually destroyed (through a process known as garbage collection). This process ensures that programmers writing Python don’t normally need to concern themselves with manually deleting an object when they’re done with it. Instead, memory is automatically freed up.

The need to keep reference counts for all objects (along with a few other mutable fields on all objects) means that there is currently no way of having a “truly immutable” object in Python.

This is a distinction that only really applies at the C level. For example, the None singleton cannot be mutated at runtime at the Python level:

>>> None.__bool__ = lambda self: True Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'NoneType' object attribute '__bool__' is read-only

However, at the C level, the object representing None is mutating constantly, as the reference count to the singleton changes constantly.

Immortal objects

An “immortal object”, according to PEP 683 (written by Elizondo/Snow), is an object marked by the runtime as being effectively immutable, even at the C level. The reference count for an immortal object will never reach 0; thus, an immortal object will never be garbage-collected, and will never die.

“The fundamental improvement here is that now an object can be truly immutable.”

Eddie Elizondo and Eric Snow, PEP 683


The lack of truly immutable objects in Python, PEP 683 explains, “can have a large negative impact on CPU and memory performance, especially for approaches to increasing Python’s scalability”.

The benefits of immortality

At their talk at the Python Language Summit, Elizondo and Snow laid out a number of benefits that their proposed changes could bring.

Guaranteeing “true memory immutability”, Elizondo explained, “we can simplify and enable larger initiatives,” including Eric Snow’s proposal for a per-interpreter GIL, but also Sam Gross’s proposal for a version of Python that operates without the GIL entirely. The proposal could also unlock new optimisation techniques in the future by helping create new ways of thinking about problems in the CPython code base.

The costs

A naive implementation of immortal objects is costly, resulting in performance regeressions of around 6%. This is mainly due to adding a new branch of code to the logic keeping track of an object’s reference count.

With mitigations, however, Elizondo and Snow explained that the performance regression could be reduced to around 2%. The question they posed to the assembled developers in the audience was whether this was an “acceptable” performance regression – and, if not, what would be?


The proposal was greeted with a mix of curious interest and healthy scepticism. There was agreement that certain aspects of the proposal would reach wide support among the community, and consensus that a performance regression of 1-2% would be acceptable if clear benefits could be shown. However, there was also concern that parts of the proposal would change semantics in a backwards-incompatible way.

Pablo Galindo Salgado, Release Manager for Python 3.10/3.11 and CPython Core Developer, worried that all the benefits laid out by the speakers were only potential benefits, and asked for more specifics. He pointed out that changing the semantics of reference-counting would be likely to break an awful lot of projects, given that popular third-party libraries such as numpy, for example, use C extensions which continuously check reference counts.

Thomas Wouters, CPython Core Developer and Steering Council Member, concurred, saying that it probably “wasn’t possible” to make these changes without changing the stable ABI. Kevin Modzelewski, a maintainer of Pyston, a performance-oriented fork of Python 3.8, noted that Pyston had had immortal objects for a while – but Pyston had never made any promise to support the stable ABI, freeing the project of that constraint.

The 2022 Python Language Summit: A per-interpreter GIL

“Hopefully,” the speaker began, “This is the last time I give a talk on this subject.”

“My name is Eric Snow, I’ve been a core developer since 2012, and I’ve been working towards a per-interpreter GIL since 2014.”

In 1997, the PyInterpreterState struct was added to CPython, allowing multiple Python interpreters to be run simultaneously within a single process. “For the longest time,” Snow noted, speaking at the 2022 Python Language Summit, this functionality was little used and little understood. In recent years, however, awareness and adoption of the idea has been spreading.

Multiple interpreters, however, cannot yet be run in true isolation from each other when run inside the same process. Part of this is due to the GIL (“Global Interpreter Lock”), a core feature of CPython that is the building block for much of the language. The obvious solution to this problem is to have a per-interpreter GIL: a separate lock for each interpreter spawned within the process.

With a per-interpreter GIL, Snow explained, CPython will be able to achieve true multicore parallelism for code running in different interpreters.

A per-interpreter GIL, however, is no small task. “In general, any mutable state shared between multiple interpreters must be guarded by a lock,” Snow explained. Ultimately, what this means is that the amount of state shared between multiple interpreters must be brought down to an absolute minimum if the GIL is to become per-interpreter. As of 2017, there were still several thousand global variables; now, after a huge amount of work (and several PEPs), this has been reduced to around 1200 remaining globals.


“Basically, we can’t share objects between interpreters”

– Eric Snow


Troubles on the horizon

The reception to Snow’s talk was positive, but a number of concerns were raised by audience members.

One potential worry is the fact that any C-extension module that wishes to be compatible with sub-interpreters will have to make changes to their design. Snow is happy to work on fixing these for the standard library, but there’s concern that end users of Python may put pressure on third-party library maintainers to provide support for multiple interpreters. Nobody wishes to place an undue burden on maintainers who are already giving up their time for free; subinterpreter support should remain an optional feature for third-party libraries.

Larry Hastings, a core developer in the audience for the talk, asked Snow what exactly the benefits of subinterpreters were compared to the existing multiprocessing module (allowing interpreters to be spawned in parallel processes), if sharing objects between the different interpreters would pose so many difficulties. Subinterpreters, Snow explained, hold significant speed benefits over multiprocessing in many respects.

Hastings also queried how well the idea of a per-interpreter GIL would interact with Sam Gross’s proposal for a version of CPython that removed the GIL entirely. Snow replied that there was minimal friction between the two projects. “They’re not mutually exclusive,” he explained. Almost all the work required for a per-interpreter GIL “is stuff that’s a good idea to do anyway. It’s already making CPython faster by consolidating memory”.

The 2022 Python Language Summit: Python in the browser

Python can be run on many platforms: Linux, Windows, Apple Macs, microcomputers, and even Android devices. But it’s a widely known fact that, if you want code to run in a browser, Python is simply no good – you’ll just have to turn to JavaScript.

Now, however, that may be about to change. Over the course of the last two years, and following over 60 CPython pull requests (many attached to GitHub issue #84461), Core Developer Christian Heimes and contributor Ethan Smith have achieved a state where the CPython main branch can now be compiled to WebAssembly. This opens up the possibility of being able to run arbitrary Python programs clientside inside your web browser of choice.

At the 2022 Python Language Summit, Heimes gave a talk updating the attendees of the progress he’s made so far, and where the project hopes to go next.

WebAssembly basics

WebAssembly (or “WASM”, for short), Heimes explained, is a low-level assembly-like language that can be as fast as native machine code. Unlike your usual machine code, however, WebAssembly is independent from the machine it is running on. Instead, the core principle of WebAssembly is that it can be run anywhere, and can be run in a completely isolated environment. This leads to it being a language that is extremely fast, extremely portable, and provides minimal security risks – perfect for running clientside in a web browser.

After much work, CPython now cross-compiles to WebAssembly using emscripten through the --with-emscripten-target=browser flag. The CPython test suite now also passes on emscripten builds, and work is going towards adding a buildbot to CPython’s fleet of automatic robot testers, to ensure this work does not regress in the future.

Users who want to try out Python in the browser can try it out at The work opens up exciting possibilities of being able to run PyGame clientside and adding Jupyter bindings.

Support status

It should be noted that cross-compiling to WebAssembly is still highly experimental, and not yet officially supported by CPython. Several important modules in the Python standard library are not currently included in the bundled package produced when --with-emscripten-target=browser is specified, leading to a number of tests needing to be skipped in order for the test suite to pass.

Nonetheless, the future’s bright. Only a few days after Heimes’s talk, Peter Wang, CEO at Anaconda, announced the launch of PyScript in a PyCon keynote address. PyScript is a tool that allows Python to be called from within HTML, and to call JavaScript libraries from inside Python code – potentially enabling a website to be written entirely in Python.

PyScript is currently built on top of Pyodide, a third-party project bringing Python to the browser, on which work began before Heimes started his work on the CPython main branch. With Heimes’s modifications to Python 3.11, this effort will only become easier.

The 2022 Python Language Summit: Performance Improvements by the Faster CPython team

Python 3.11, if you haven’t heard, is fast. Over the past year, Microsoft has funded a team – led by core developers Mark Shannon and Guido van Rossum – to work full-time on making CPython faster. With additional funding from Bloomberg, and help from a wide range of other contributors from the community, the results have borne fruit. On the pyperformance benchmarks at the time of the beta release, Python 3.11 was around 1.25x faster than Python 3.10, a phenomenal achievement.

But there is more still to be done. At the 2022 Python Language Summit, Mark Shannon presented on where the Faster CPython project aims to go next. The future’s fast.

The first problem Shannon raised was a problem of measurements. In order to know how to make Python faster, we need to know how slow Python is currently. But how slow at doing what, exactly?

Good benchmarks are vital for a project that aims to optimise Python for general usage. For that, the Faster CPython team needs the help of the community at large. The project “needs more benchmarks,” Shannon said – it needs to understand more precisely what the user base at large is using Python for, how they’re doing it, and what makes it slow at the moment (if it is slow!).

A benchmark, Shannon explained, is “just a program that we can time”. Anybody with a benchmark – or even just a suggestion for a benchmark! – that they believe is representative of a larger project they’re working on is invited to submit them to the issue tracker at the python/pyperformance repository on GitHub.

Nonetheless, the Faster CPython team has plenty to be getting on with in the meantime.

Much of the optimisation work in 3.11 has been achieved through the implementation of PEP 659, a “specializing adaptive interpreter”. The adaptive interpreter that Shannon and his team have introduced tracks individual bytecodes at various points in a program’s execution. When it spots an opportunity, a bytecode may be “quickened”: this means that a slow bytecode, that can do many things, is replaced by the interpreter with a more specialised bytecode that is very good at doing one specific thing. The work on PEP 659 has now largely been done, but major parts, such as dynamic specialisations of for-loops and binary operations, are still to be completed.

Shannon noted that Python also has essentially the same memory consumption in 3.11 as it did in 3.10. This is something he’d like to work on: a smaller memory overhead generally means fewer reference-counting operations in the virtual machine, a lower garbage-collection overhead, and smoother performance as a result of it all.

Another big remaining avenue for optimisations is the question of C extensions. CPython’s easy interface with C is its major advantage over other Python implementations such as PyPy, where incompatibilities with C extensions are one of the biggest hurdles for adoption by users. The optimisation work that has been done in CPython 3.11 has largely ignored the question of extension modules, but Shannon now wants to open up the possibility of exposing low-level function APIs to the virtual machine, reducing the overhead time of communicating between Python code and C code.

Is that a JIT I see on the horizon?

Lastly, but certainly not least, Shannon said, “everybody wants a JIT compiler… even if it doesn’t make sense yet”.

A JIT (“just-in-time”) compiler is the name given for a compiler that dynamically detects where performance bottlenecks exist in a program as the program is running. Once these bottlenecks have been identified, the JIT compiles these parts of the program on-the-fly into native machine code in order to speed things up. It’s a similar idea to Shannon’s PEP 659, but goes much further, since the specialising adaptive interpreter never goes beyond the bytecode level.

The idea of using a JIT compiler for Python is hardly new. PyPy’s JIT compiler is the major source of the large performance gains the project has over CPython in some areas. Third-party projects, such as pyjion and numba, bring just-in-time compilation to CPython that’s just a pip install away. Integrating a JIT into the core of CPython, however, would be materially different.

Shannon has historically voiced scepticism about the wisdom of introducing a JIT compiler into CPython itself, and said that work on introducing one is still some way off. A JIT, according to Shannon, will probably not arrive until 3.13 at the earliest, given the amount of lower-hanging fruit that is still to be worked on. The first step towards a JIT, he explained, would be to implement a trace interpreter, which would allow for better testing of concepts and lay the groundwork for future changes.

Playing nicely with the other Python projects

The gains Shannon’s team has achieved are hugely impressive, and likely to benefit the community as a whole in a profound way. But various problems lie on the horizon. Sam Gross’s proposal for a version of CPython without the Global Interpreter Lock (the nogil fork) has potential for speeding up multithreaded Python code in very different ways to the Faster CPython team’s work – but it could also be problematic for some of the optimisations that have already been implemented, many of which assume that the GIL exists. Eric Snow’s dream of achieving multiple subinterpreters within a single process, meanwhile, will have a smaller performance impact on single-threaded code compared to nogil, but could still create some minor complications for Shannon’s team.

The 2022 Python Language Summit: Upstreaming optimisations from Cinder

In May 2021, the team at Instagram made waves in the world of Python by open-sourcing Cinder, a performance-oriented fork of CPython.

Cinder is a version of CPython 3.8 with a ton of optimisations added to improve speed across a wide range of metrics, including “eager evaluation of coroutines”, a just-in-time compiler, and an “experimental bytecode compiler” that makes use of PEP 484 type annotations.

Now, the engineers behind Cinder are looking to upstream many of these changes so that CPython itself can benefit from these optimisations. At the 2022 Python Language Summit, Itamar Ostricher, an engineer at Instagram, presented on Cinder’s optimisations relating to async tasks and coroutines.

Asyncio refresher

Consider the following (contrived) example. Here, we have a function, IO_bound_function, which is dependent on some kind of external input in order to finish what it’s doing (for example, this might be a web request, or an attempt to read from a file, etc.). We also have another function, important_other_task, which we want to be run in the same event loop as IO_bound_function

import asyncio async def IO_bound_function(): """This function could finish immediately... or not!""" # Body of this function here async def important_other_task(): await asyncio.sleep(5) print('Task done!') async def main(): await asyncio.gather( IO_bound_function(), important_other_task() ) print("All done!") if __name__ == "__main__":

IO_bound_function could take a long time to complete – but it could also complete immediately. In an asynchronous programming paradigm, we want to ensure that if it takes a long time to complete, the function doesn’t hold up the rest of the program. Instead, IO_bound_function will yield execution to the other thing scheduled in the event loop, important_other_task, letting this coroutine take control of execution for a period.

So far so good – but what if IO_bound_function finishes what it’s doing immediately? In that eventuality, we’re creating a coroutine object for no reason at all, since the coroutine will never have to suspend execution and will never have to reclaim control of the event loop at any future point in time.

Call me maybe?

The team at Instagram saw this as an optimisation opportunity. At the “heart” of many of their async-specific improvements, Itamar explained, is an extension to Python’s vectorcall protocol: a new _Py_AWAITED_CALL_MARKER flag, which enables a callee to know that a call is being awaited by a caller.

The addition of this flag means that awaitables can sometimes be eagerly evaluated, and coroutine objects often do not need to be constructed at all.

Ostricher reported that Instagram had seen performance gains of around 5% in their async-heavy workloads as a result of this optimisation.

Pending questions

Significant questions remain about whether these optimisations can be merged into the main branch of CPython, however. Firstly, exact performance numbers are hard to come by: the benchmark Ostricher presented does not isolate Cinder’s async-specific optimisations.

More important might be the issue of fairness. If some awaitables in an event loop are eagerly evaluated, this might change the effective priorities in an event loop, potentially creating backwards-incompatible changes with CPython’s current behaviour.

Lastly, there are open questions about whether this conflicts with a big change to asyncio that has just been made in Python 3.11: the introduction of task groups. Task groups – a concept similar to “nurseries” in Trio, a popular third-party async framework – are a major evolution in asyncio’s API. But “it’s not completely clear how the Cinder optimisations might apply to Task Groups,” Ostricher noted.

Ostricher’s talk was well received by the audience, but it was agreed that discussion with the maintainers of other async frameworks such as Trio was essential in order to move forward. Guido van Rossum, creator of Python, opined that he could “get over the fairness issue”. The issue of compatibility with task groups, however, may prove more complicated.

Given the newness of task groups in asyncio, there remains a high degree of uncertainty as to how this feature will be used by end users. Without knowing the potential use cases, it is hard to comment on whether and how optimisations can be made in this area.