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Releases: mu-editor/mu

Snek and fixes.

15 Nov 10:25
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This release introduces Snek mode, fixes some minor bugs, addresses some usability gremlins and adjusts some capabilities to make things tidier. Much of this work was done over the summer at the code-sprints at EuroPython 2022 in Dublin. Kudos and thanks to all the new contributors to Mu.

Please provide bug reports or feedback via:

  • Thanks to @keith-packard for Snek mode. Snek is a Python inspired language for processors too small even to run MicroPython.
  • @tmontes contributed changes so Mu builds to Linux AppImages (an easy way to package application for Linux).
  • Minor fixes by @stratakis in the Russian translation.
  • @carlosperate fixed many minor glitches and gremlins.
  • @carlosperate was on fire 🔥 with fixes needed to ensure Mu continues to work with very old versions of OSX (as used in many educational institutions).
  • Again, thanks to @carlosperate, AppImage with Wayland no longer the setting of an environment variable to make it work properly.
  • The web mode includes simple and easy to use integration with beginner and education friendly web hosts, PythonAnywhere.
  • @agdales, @Jeffrey04, @johannaengland and @AnjaVerboven contributed new messages of the day as part of their onboarding at EuroPython.
  • @tonybaloney contributed several Windows based fixes and clean-ups.
  • @johannaengland and @prcutler were on fire tidying up and fixing docs at EuroPython.
  • A bug was fixed in the web mode relating to the resolution and/or recreation of the assets directory (in which images, css and templates were to be found).
  • Or friend at Adafruit, @tannewt made the necessary changes so Mu handles OSC commands gracefully (see the PR for more details).
  • New contributor, @zigit ensured "Unexpected Maker" based ESP boards are correctly detected.
  • Thanks to @Jayman2000, error messages are correctly capitalized (or not) to avoid potential confusion.

1.1.1 stable

22 Feb 17:17
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This is the first stable release of the 1.1.* version of Mu. The following changes have been made since the last beta:

  • Minor clean ups in the Makefile.
  • Thank you to @microbit-mark for updating the board IDs to support version 2.2 of the device.
  • Updates to the Chinese translation by @CSharperMantle. 謝謝。
  • Updates to the Slovak translation by @bletvaska. Ďakujem.
  • The foundations of a brand new Russian translation of Mu by @grovz with contributions from @iamdbychkov. спасибо!
  • Thanks to @MinoruInachi (with feedback from @odaki) for a revised Japanese translation for Mu. ありがとうございます
  • Due to complicated dependency problems, we've updated the bundled version of Flask to 2.0.3. Thanks to @carlosperate for quickly resolving this problem.
  • Due to limitations in the way Windows MSI installers work, we're releasing this version as 1.1.1 (rather than 1.1.0).

Many thanks to everyone who has worked so diligently getting to this stable release.

Translations, bug fixes and updates

22 Dec 11:36
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  • We expect this release to be the last beta before the final 1.1 release in the new year of 2022. Season's greetings to everyone using or contributing to Mu, and here's wishing you all a flourishing and fulfilling 2022.
  • As always there have been the usual minor bug fixes and clean ups from the core team of maintainers. Thank you so much for all that you do to support the continued development of Mu.
  • Thanks to the ever-green @keith-packard for his contribution to ensure icons on the button bar continuously scale based on the window width. This looks really smooth and slick.
  • Tinsel laden @tmontes has made a number of contributions around tooling for internationalization (i18n) of Mu. These include using the
    Babel package for generating the required translation files from our source code, and updating the Makefile (and so the process can be automated.
  • Xmassy @xbecas is a new joiner to the core team and we're very please to have him with us since he has done a huge amount of work on updating and curating the translation files needed for i18n. Thanks to his work, translators for all the other existing locales need not have to go through the string generation/update steps (he's done that for you already!).
  • Both @xbecas and @tmontes have made extensive updates to our pt-PT (Portuguese) translation. Feliz Natal e Próspero Ano Novo.
  • This was swiftly followed by a welcome contribution by @rffontenelle the red-nosed translator, who made extensive updates to the pt-BR (Brazilian Portuguese) translation. Many thanks Rafael, you continue to demonstrate why the Brazilian FLOSS community is such a vibrant place, and we hope your work will help beginner coders in Brazil take their first steps to join your community. Boas Festas!
  • Now that the upstream PyGame / PyGameZero packages have been updated and repackaged, @tmontes has ensured we use these (rather than our own custom builds) in our installers for Windows and OSX. Many thanks to our friends and collaborators in those projects (cc/ @illume and @lordmauve).
  • Once in royal @devdanzin's repos, stood some lowly bugs to fix. These include ensuring empty path handling is properly handled by get_save_path, correct highlighting of both f-strings and triple quoted strings in the editor widget, fixing a comment-toggling bug that deleted the first character of the next line under certain circumstances and more robust handling of environment variables. Wow, @devdanzin was on fire..! (...and has further work in development, thank you so much for your continued contributions.)
  • Carolling @carlosperate has put a huge effort in. He has triaged various crash reports, administered our continuous integration pipeline, and reviewed and merged much of the work described above. He also ensured our version numbering for Mu is no longer odd, and meets the guidelines set out in PEP440.
  • Good Tim Golden (@tjguk) fast typed out, a venv that's crisp and even. His outstanding work on making Python virtual environments work in some of the most inhospitable computing environments ever found is miraculous. Tim's genius is to know exactly the right intervention to make, and in this case his epic addition of -I to the Mu codebase will help ensure the user's virtual environments are properly isolated.
  • @TMonter has updated the pup packager we use to create our installer. This should fix a problem found on the new ARM based Macs. He has also made significant progress on a cross-distro Linux package which we hope will make an appearance in the not-too-distant future.
  • Finally, Nicholas (@ntoll) promises never to do another Christmas themed changelog. 🎄 🎅 🎉

Lots of improvements, manual locale, Crostini on Chromebooks etc...

06 Oct 07:57
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  • There have been the usual minor bug fixes and clean ups from various regular contributors and some new ones too. Thank you for your careful and well targetted changes.
  • Carlos (@carlosperate) fixed some packaging problems relating to the iPython kernel bundled with Mu.
  • Martin (@dybber) fixed a couple of problems relating to the stopping of child processes (Flask and scripts stopped via KeyboardInterrupt in Linux).
  • The web mode checks for the availability of templates in the local directory tree before starting up. If a template directory isn't found in the expected location, then the user sees a helpful message describing the problem and what they need to do to fix it.
  • Mu's splash screen no longer always appears on top of everything else on the user's desktop. The splash screen now also logs the progress of installing the various packages needed on first install. Thanks to Carlos for these changes.
  • A new admin/settings option has been added to allow users to manually change the translation Mu uses for its interface. Updating this setting requires a restart of Mu. Zander (@ZanderBrown) contributed the icon/glyph to indicate the relevant tab is for translation related settings (not entirely obvious if Mu's UI is using a language you don't understand and you're looking for the setting that relates to translations). The icon makes this clear.
  • On some desktop windowing systems there is a bug that means windows re-open at a position higher up the screen, and so may appear off the top of the screen. We've ensured this never happens with Mu. If Mu starts with any part of the window off the screen, the window is moved to be within the dimensions of the screen. This was a weird one to track down and fix.
  • Many thanks to Ethan Spoelstra (@espoelstra) who contributed a change so Crostini on ChromeOS is used to return the correct CIRCUITPY path if it exists.
  • Huge thanks to Keith Packard (@keith-packard) for several contributions to this release of Mu. Keith refactored the way in which Mu handles pasting in the REPL window so it works correctly and more broadly across operating systems.
  • Keith also fixed some font related issues in the REPL.
  • Keith was on fire with a couple more contributions relating to SVG icons in the buttons in Mu. We're very grateful to Ben Williams (@Rybec) for putting in the work to make our button icons SVG files. Keith made the code changes to implement this.
  • Thanks to Miro Hrončok (@hroncok) for pointing out a change in Python 10 which would break some of our UI calls into PyQt, and who provided a patch to fix things.
  • Some minor clarifications in our developer documentation (

Venv updates, New micro:bit MicroPython, Adafruit Apple M1 fix

05 Jul 08:02
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  • Several of us made minor updates and fixes (such as ensuring various packages had explicit dependency versions listed, updating versions for Mu's own dependencies and so on).
  • Right clicking on highlighted text in the editor, with the REPL active, now has an additional option added to the context menu: to correctly paste the text from the editor into the REPL. Thanks to Professor Chris Rogers of Tufts University for suggesting this feature.
  • The multi-talented Dan Halbert (@dhalbert) of Adafruit very kindly fixed a bug in the Adafruit board handling when on run on new Apple M1 hardware. Thank you Dan for your valuable contribution.
  • A huge amount of work by Tim (@tjguk) and Carlos (@carlosperate) has gone into analysing the crash reports from recent beta releases of Mu. This has resulted in significant effort to address many of the bugs encountered, many of which related to edge cases encountered by the new virtual environment feature. Tim and Carlos have created many fixes and checks to ensure these bugs are either completely fixed or are, at least, mitigated in more helpful ways. This has been a challenging and "fiddly" bit of work, so kudos and thanks, as always, to both Tim and Carlos for their continued efforts.
  • Carlos has also updated the version of MicroPython used in the BBC micro:bit mode to the latest 2.0.0-beta.5 version.
  • In addition, Carlos has ensured that the micro:bit mode flashes files onto the micro:bit using the correctly memory aligned hex string.
  • Github user @ajs256 has ensured the crash reporter doesn't kick in when a KeyboardInterrupt is triggered in Mu (CTRL-C).
  • Sometimes in Mu for Linux, the expected .py file extension wasn't added to new files. This depended on the user's graphical shell. Mu now checks the output from the shell and, if requires, will add .py itself.
  • Various fixes to Mu's logging make it more robust, clear and useful.
  • Tiago (@tmontes) fixed a late breaking bug in packaging Mu for OSX. All fixed in a matter of hours. Amazing work!

Third Public Beta - packaging cleanup, logging, new CircuitPython enhancements

18 Apr 20:17
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  • Carlos made many changes to clean up the specification for required modules used by the installer. This will make supporting and tracking Mu's dependencies MUCH easier. Thank you Carlos!
  • Huge thanks to Dan Halbert of Adafruit who contributed a significant amount of refactoring to the CircuitPython mode. As a result Mu now uses the adafruit-board-toolkit module for device identification, among many other helpful changes described in Dan's pull request. Thank you Dan..!
  • Carlos was on fire... he also fixed a bug in the file-copy dialog when the context menu was opened with an empty list of files.
  • Carlos (again), fixed some outstanding documentation issues for supporting Raspbian Buster (and newer). These are now at
  • Carlos (again, again) tidied up various aspects of the Makefile so there is only a single source of truth for running various utilities and commands.
  • Logging was another focus for this release. Now that we have a few weeks worth of crash reports we've been able to look at the parts of the application that cause most grief and add extra-logging in various locations. Tim put in a great effort to make sure the "first run" and other virtual environment based aspects of Mu now have clearer and more useful logging and throw more useful exceptions, closer to the source of the problem, for the resulting crash report. Carlos ensured the IPython kernel installation was properly logged.
  • We ensured various key packages were pinned to particular versions to maximise compatibility with older versions of Python still found in schools.

1.1.0-beta.3 - Second Public Beta. Bug fixes and Splash Screen

29 Mar 10:13
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This is a beta release and may contain bugs or unfinished features. Please
provide bug reports or feedback via:

  • During beta phase, we're moving to a fortnightly release cadence. Expect beta 4 on around the 12th April.
  • The final version of the Mu splash screen was delivered. Huge thanks to the extraordinarily talented Steve Hawkes (@hawkz) of The Developer Society for his generous artistic support, patience and humorous approach.
  • Thanks to a recent update in PyGame Zero, we're back to using the official package from PyPI, rather than our patched fork, in the installer.
  • Both Tim and Carlos have contributed updates, fixes and tests to address a bug affecting Windows users who may have a space in the file path upon which Mu is found. This was a difficult bug to reproduce but Tim did a lot of digging to isolate the cause with as much confidence as is possible when it comes to such things. Carlos did a bunch of thankless and fiddly test related work so testing with spaces in the path is part of our test suite. Work on this is ongoing so expect further improvements in upcoming releases. As always, many thanks for these efforts.
  • Tim addressed a wheel/sdist related problem that was causing odd side effects with regard to dependancies.
  • A strange bug, where it was not possible to install third-party packages on first run of Mu, opened up a deep rabbit hole of investigation. In the end Tim was able to fix this AND address the source of a warning message from Qt when Mu was starting for the first time.
  • The splash screen code was rewritten in such a way that objects relating to the splash screen will always be garbage-collected by Python and destroyed by Qt5. Previously, they existed for the full duration of the application, not really causing any problems, but "in limbo" nonetheless.
  • The crash reporting tool has had a minor update so the user is reminded to attach their log file to the bug report, along with an indication of where to find the log file.

1.1.0-beta.2 - First Public Beta

15 Mar 12:12
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From the release notes:

  • This is the first public beta release (beta 1 was created for testing by the core development team).
  • Many minor bug fixes to the existing new features found in beta 1 (see below).
  • Many thanks to Martin Dybdal for his work on improving the admin panel.
  • Carlos made significant changes so Mu can be packaged with very recent versions of Python. Carlos also made various changes relating to the status of Python packages contained within the official installer.
  • Many thanks to Dan Pope for assistance with an upgraded version of PyGameZero (which uses the latest version of PyGame - kudos to René and the other developers of PyGame for the recent improvements).
  • Various fixes to the UI so that panes are easier to resize and the themes are correctly applied to the REPL (thanks again to Martin for these fixes).
  • Carlos also contributed fixes relating to the micro:bit mode (compatibility with versions 1 and 2).
  • Tim has made herculean efforts to ensure the creation and checking of Mu's virtual environment is robust and easy to maintain.
  • A new crash reporting feature has been added. If Mu breaks the user will be redirected to the endpoint with details of the crash and an option to create a bug report. This ensures Mu crashes are handled more gracefully, and the user is able to see the error that caused the crash.
  • A new animated splash screen has been added so the initial creation of Mu's virtual environment happens in such a way that the user can see progress is being made, and updates are logged on the splash screen for the user. If Mu encounters a problem at this early stage, the splash screen recovers and the new crash reporting feature kicks in. The current animation was created by Steve Hawkes (thank you) with a much more polished version promised very soon..!
  • Behind the scenes, Tiago has continued to make outstanding work on the pup tool we use to create the installers for Windows 64/32 bit and MacOS X. This beta release will be the first to use installers created with pup.
  • Known bug - on first ever start of Mu, if in Python3 mode the package manager will not work. Re-starting Mu fixes this (i.e. from second and subsequent starts). We're tracking this problem via this issue.


31 Jan 20:37
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1.1.0-beta.1 Pre-release


  • A new mode for ESP8266/ESP32 devices running MicroPython. This work and a significant amount of related refactoring was contributed with Viking like energy and efficiency by Martin Dybdal. This work has meant it was relatively easy to create two further new modes...
  • New mode for Lego Spike devices (thanks to Chris and Ethan at Tufts University for the help and support).
  • New mode for Raspberry Pi Pico (thanks to Zander, Martin and Carlos for the extensive testing).
  • Updates to the Microbit mode made by Spanish source-code wrangler extraordinaire (and resident Microbit expert) Carlos Pereira Atencio. The Microbit mode now supports versions 1 and 2 of the board.
  • Various bits of artwork used in the application have been updated (including a new [temporary] animated splash screen). Thanks to devdanzin for choreographing the initial work on the splash screen at short notice.
  • A complete re-write of the virtualenv and third party package handlers by the hugely talented Tim Golden. This was a long term and difficult refactoring project which Tim has delivered with great aplomb. This should make package handling much smoother and simpler.
  • Various smallish UI fixes, enhancements and smoothing by devdanzin. Thank you for these contributions - they really make a difference to the ease of use and friendly feel of Mu.
  • This version of Mu is packaged with stand-alone installers for Windows and OSX by the wonder that is PUP - a new packaging tool by our very own Tiago Montes ~ Portugal's Premier Python Packager Par-excellence. We have big plans for PUP... watch this space. :-)
  • Many many many minor bug fixes contributed by many many many people to whom we are eternally grateful.


26 Jan 21:21
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This is a bugfix release to address OSX Catalina changes which caused Mu to render incorrectly.

Full list of the (minor) changes can be found in the changelog here:

Please see the website here: Developer documentation here: Project blog here: