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Dec 27, 2019
Feb 9, 2018

Mnemosyne: Optimized Flashcards and Research Project

Mnemosyne is:

  • a free, open-source, spaced-repetition flashcard program that helps you learn as efficiently as possible.
  • a research project into the nature of long-term memory. If you like, you can help out and upload anomynous data about your learning process (this feature is off by default).

Important features include:

  • Bi-directional syncing between several devices
  • Clients for Windows/Mac/Linux and Android
  • Flashcards with rich content (images, video, audio)
  • Support for Google text-to-speech and Google translate
  • Powerful card types
  • Flexible card browser and card selection
  • Visualization to illustrate your learning process
  • Extensive plugin architecture and external scripting
  • Different learning schedulers
  • Webserver for review through browser (does not implement any security features so far)
  • Cramming scheduler to review cards without affecting the regular scheduer
  • Core library that allows you to easily create your own front-end.

You can find a more detailed explanation of the features on the webpage, as well as the general documentation.

If you just want to download the latest Mnemosyne release as a regular user, please see the Download section. If you are interested in running and changing the latest code, please read on.

Installation of the development version and hacking

We use the git version control system and Github to coordinate the development. Please use a search engine to find out how to install git on your operating system. If you are new to git and github, there are many tutorials available on the web. For example, this interactive tutorial. See also section working locally with the code and sharing your changes for some info about git and Github.

About the code base

To get an overview of how all the different bits of the library fit together, see the documentation in the code at mnemosyne/libmnemosyne/docs/build/html/index.html. In order to keep the code looking uniform, please following the standard Python style guides PEP8 and PEP257.

Running the development code

You can find instructions for Windows here. The following instructions are valid for Linux and Mac (if you use homebrew or some other package manager).

Runtime requirements

To start working on Mnemosyne, you need at least the following software.

  • Python 3.5 or later
  • PyQt 5.6 or later, including QtWebEngineWidgets.
  • Matplotlib
  • Easyinstall
  • cheroot 5 or later
  • Webob 1.4 or later
  • Pillow
  • gTTS for Google text-to-speech
  • googletrans for Google translate support
  • argon2-cffi
  • For Latex support: the latex and dvipng commands must be available (e.g., TeXLive on Linux, MacTeX on Mac, and MikTeX on Windows). On Arch based distributions, you'll need texlive-core package too.
  • For building the docs: sphinx (If you get sphinx-related errors, try installing sphinx as root)
  • For running the tests: nose

You can either run a development version of Mnemosyne by using your system-wide Python installation, or by using a virtual environment with virtualenv. If your distribution provides and packages all necessary libraries in a recent enough version, using the system-wide Python install is probably easier and the recommended way.

Using the system-wide python installation

First, install all dependencies with your distribution's package manager. Then, run make build-all-deps, followed by make from the top-level mnemosyne directory. This will generate all the needed auxiliary files and start Mnemosyne with a separate datadir under dot_mnemosyne2. If you want to use mnemosyne interactively from within a python shell, run python from the top-level mnemosyne directory. You can check if the correct local version was imported by running import mnemosyne; print(mnemosyne.__file__).

Using a local python installation

If your distribution does not provide all required libraries, or if the libraries are too old, create a virtual environment in the top-level directory (virtualenv venv), activate it (source venv/bin/activate) and install all the required dependencies with pip install. Then, follow the steps of the previous paragraph.

Running the test suite

You can always run the test suite:

make test


python3 -m nose --exe tests

Single tests can be run like this:

python3 -m nose --exe tests/<file_name>.py:<class_name>:<method_name>

Nose captures stdout by default. Use the -s switch if you want to print output during the test run.

You can increase the verbosity level with the -v switch.

Add --pdb to the command line to automatically drop into the debugger on errors and failures. If you want to drop into the debugger before a failure, edit the test and add the following code at the exact spot where you want the debugger to be started:

from import set_trace; set_trace()

System-wide installation from source

For testing the development version it is not necessary to do a system-wide installation. If you want to do so anyway, here are the instructions.


Follow the installation instructions from above (install the dependencies, get the source code - either by cloning it from github, or by downloading and extracting the .tar.gz archive). Then, run the following command from within the top-level directory of the repository (which is also the location of this file):

sudo python install

Depending on your setup, you might need to replace python with python3. To test the installation, change to any other directory and run mnemosyne. For example:

cd ~

If you run into the issue of non-latin characters not displaying on statistic plots, install ttf-mscorefonts-installer and regenerate the font cache of matplotlib.


  • Download and install Homebrew (see
  • Create a CODESIGN_IDENTITY certificate as described at
    • Open Applications > Utilities > Keychain Access
    • From the Keychain Access menu, choose Certificate Assistant > Create a Certificate
    • Name: something unique, I used "Devin Howard - Mnemosyne".
    • Identity Type: Self Signed Root
    • Certificate Type: Code signing
    • when you run "make macos" below, ensure you have set the CODESIGN_IDENTITY environment variable to the Name you chose above. For example, I run it like export CODESIGN_IDENTITY="Devin Howard - Mnemosyne" make clean make macos
    • But you might instead run export CODESIGN_IDENTITY="My Cool Certificate" make clean make macos
  • Open the Terminal.
  • Make sure you are using the latest version of Homebrew:
brew update
  • Install dependencies for Mnemosyne.
brew install python@3.9 qt@5 mplayer openjpeg libffi
brew install --cask xquartz # needed for mplayer dylibs
  • For Mnemosyne 2.8, we used Python 3.9.13 and Qt 5.15.3. To confirm you're using the correct versions:
python3 --version
brew list --versions qt@5
  • If the versions are not correct, and you need to edit a Homebrew dependency, you can use these commands:
brew uninstall <package-name>
brew edit <package-name>
# Example: replace the file with the contents of and save it
brew install <package-name>
brew pin <package-name>
  • Create a python virtual environment to isolate python dependencies from the rest of your system:
pip3 install virtualenv
virtualenv --python=python3 venv
source venv/bin/activate

From now on, your shell should have a (venv) at the beginning indicating you're inside the virtual environment. Ensure the copy of pip in the virtual environment is at least version 21.1.1 or later:

pip --version

If not, upgrade pip with

pip install --upgrade pip
  • Install the python dependencies for Mnemosyne
  • Note for Mnemosyne 2.8, we used PyQt5 5.15 and PyInstaller 5.1
pip install argon2-cffi cheroot googletrans gtts matplotlib numpy pillow pyopengl sip tornado webob 

# run this command and inspect the output to confirm you're using the correct versions
pip install pyqt5 pyqtwebengine pyinstaller
  • Build it (while still using the python virtual environment):
export CODESIGN_IDENTITY="Devin Howard - Mnemosyne" # see note above about CODESIGN_IDENTITY
make clean
make macos
  • Test the new application (back up your data directory first!):
open dist/
  • Optionally drag and drop this new app to /Applications.

Git and Github info

Github CLI Tool

If you're planning on contributing more than one pull request using Git and Github, you might find to be a useful tool for managing your repositories, forks, pull requests, and branches.

Working locally with the code

If you want to hack on Mnemosyne and propose your changes for merging later ('pull request'), first create an account on, or log into, Github. Then, fork the project on Github. You now have your own copy of the Mnemosyne repository on Github.

To work with the code, you need to clone your personal Mnemosyne fork on Github fork to your local machine. It's best to setup ssh for Github, but you don't have to. Change to your working directory on the terminal and then clone your repository of Mnemosyne (in this example without ssh):

git clone<your-username>/mnemosyne.git

Let's also make it easy to track the official Mnemosyne repository:

git remote add upstream

It is best to create your own branches for your work:

git checkout -b <branch name>

Whenever you want, you can commit your changes:

git status
git add <files to add>
git commit -v

Sharing your changes

At some point you may want to share your changes with everyone. Before you do so, you should check make sure that you didn't introduce new test failures. Then, you should check if changes were made to the original Mnemosyne repository on Github. Your private fork on Github is not automatically updated with these changes. You can get the most recent changes like this:

git fetch upstream
git checkout master
git merge upstream/master

If there are new changes, your repository now looks like this (each number symbolises a commit):

your local master branch:  ---1-2-3-4'-5'-6'-7'-8' (new changes from upstream)
your local feature branch:        |-4-5-6 (your changes)

Before you push your branch, you should rebase it on master. Rebasing takes all the changes in your branch (in the figure: 4-5-6) and tries to apply them on top of the master branch, so that we end up with a linear history:

your local master branch:  ---1-2-3-4'-5'-6'-7'-8' (new changes from upstream)
your local feature branch:                      |-4-5-6 (your changes)

Rebase like this:

git checkout <branch name>
git rebase master

Follow the instructions (git status gives additional information). Once you've successfully rebased your branch, push it to your Github account (we use --force, because we want to overwrite the existing branch on our private Github account):

git push origin --force <branch name>

To create a pull request for your changes, go to the Mnemosyne project page on Github and click on the pull request tab. Click on 'New pull request' and follow the instructions.

Finally, some more background on the whole workflow can be found here.