A "micro" editor for MicroPython and the BBC micro:bit. Written in Python and Qt5.
Python Other
Latest commit 50b1a00 Jan 18, 2017 @ntoll ntoll committed on GitHub Merge pull request #229 from mu-editor/travis_osx_py35
Force Travis OS X to install Python 3.5


Mu - a "micro" editor

This project works with Python 3 and the Qt UI library.

Currently, the latest builds for Windows, OSX and Linux x86 can be found here:



You could run Mu from source. Alternatively, go to the link above, choose the directory for your platform and download the latest build of the editor (HINT: they're ordered by date).


You only need to copy the downloaded .exe file somewhere handy and double-click it to launch. Once you've got past all the Windows induced warnings and privilege requests you'll see the editor. Unfortunately, due to Windows more than anything else, to be able to use the REPL you'll need to install a driver for USB/serial connectivity to the BBC micro:bit. You can find the required driver and detailed instructions for installing it on ARM's website:


We're trying to find a way around this problem via Windows packaging.


OSX will probably ask you to confirm you want to run a program downloaded from the internet. You may need to right-click on the file and select open to make it work first time. You do not need to install any drivers.


Just make the file executable and run it! :-)

We're in the process of creating official packages for both Debian and Fedora based flavours of Linux.

Raspberry Pi (Raspbian)

A package is available for Raspbian for mu can be installed using the following commands.

Open a Terminal (Menu > Accessories > Terminal):

sudo apt-get update

sudo apt-get install mu


Mu is a very simple code editor for kids, teachers and beginner programmers. It's written in Python and works on Windows, OSX, Linux and Raspberry Pi.


There isn't a cross platform Python code editor that is:

  • Easy to use;
  • Accessible to everyone;
  • Available on all major platforms;
  • Well documented (even for beginners);
  • Simply coded;
  • Currently maintained; and,
  • Thoroughly tested.

Mu addresses these needs.

In the Python world, teachers, students and other beginner programmers are forced to use one of the following options:

  • IDLE - the long-in-the-tooth, unmaintained and eccentric editor that comes with Python.
  • A third party IDE (integrated development environment) for teaching. If "IDE" sounds complicated, that's because it is.
  • A professional programmer's editor such as vi or emacs.

Such tools are fiddly, complicated and full of distracting "features". They are completely inappropriate for teaching and learning ~ complexity impedes a novice programmer's first steps.


Mu's outlook is:

  • Less is more (remove all unnecessary distractions);
  • Keep it simple (so Mu is easy to understand);
  • Walk the path of least resistance (Mu should be easy);
  • Have fun (learning should be a positive experience).

Our first iteration targets MicroPython on the BBC micro:bit.

The BBC's micro:bit project is aimed at 11-year old children. It consists of a small and simple programmable device. One option is the remarkable work of Damien George in the form of MicroPython, a full re-implementation of Python 3 for microcontrollers including the BBC micro:bit.

The BBC's "blessed" solution for programming this device is web-based. However, we have observed that this doesn't provide the optimum experience for Python:

  • It requires you to use a web-browser as a text based code editor.
  • You need to download the .hex file to flash onto the device and then drag it to the device's mount point on the filesystem. A rather clunky multi-part process.
  • It doesn't allow you to connect to the device in order to live code in Python via the REPL.

The Mu editor addresses each of these problems: it is a native application specifically designed as a text based coding environment. It makes it easy to flash your code onto the device (it's only a click of a button). It has a built in REPL client that automatically connects to the device.

Mu has been adapted from my previous work done with Damien George and Dan Pope on the "Puppy" editor for kids. Mu is an ultra-slimmed down version of Puppy.

The code is simple and monolithic - it's commented and mostly found in a a few obviously named Python files. This has been done on purpose: we want teachers and kids to take ownership of this project and organising the code in this way aids the first steps required to get involved (everything you need to know is in four obvious files).

In terms of features - it's a case of less is more:

  • Create a new Python script.
  • Load an existing Python script.
  • Save the existing Python script.
  • Flash the device with the current script.
  • Connect to the device via the REPL (will only work if a device is connected).
  • Zoom in/out.
  • Day / night (high contrast) modes.
  • Built in help (HTML).
  • Quit.

That's it!


If you only want to use Mu then please ignore this section. If you'd like to contribute to the development of Mu read on...

The source code is hosted on GitHub. Please feel free to fork the repository. Assuming you have Git installed you can download the code from the canonical repository with the following command:

$ git clone https://github.com/mu-editor/mu.git

For this to work you'll need to have Qt5 and Python 3 installed.

  • On Debian based systems this is covered by installing: python3-pyqt5, python3-pyqt5.qsci and python3-pyqt5.qtserialport.

  • On Mac OS, first install PyQT5:

    brew install pyqt5 --with-python3

    Then install QScintilla using the recipe from the mu repository:

    brew install https://raw.githubusercontent.com/mu-editor/mu/master/package/extras/qscintilla2.rb


    If you have an existing virtual environment it will not have changed to add the new packages. The simplest thing to do is to create a new virtual environment, remembering to use the --system-site-packages switch so that installed libraries are included. For instance:

    $ virtualenv -p /usr/local/bin/python3 --system-site-packages ~/env/py3


    $ mkvirtualenv -p /usr/local/bin/python3 --system-site-packages py3

Ensure you have the correct dependencies for development installed by creating a virtualenv and running:

$ pip install -r requirements.txt

To run the local development version of "mu", in the root of this repository type:

$ python3 run.py

There is a Makefile that helps with most of the common workflows associated with development. Typing "make" on its own will list the options thus:

$ make

There is no default Makefile target right now. Try:

make clean - reset the project and remove auto-generated assets.
make pyflakes - run the PyFlakes code checker.
make pep8 - run the PEP8 style checker.
make test - run the test suite.
make coverage - view a report on test coverage.
make check - run all the checkers and tests.
make docs - run sphinx to create project documentation.

Before contributing code please make sure you've read CONTRIBUTING.rst.