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What if it did not work?

In the following we list some common problems and solutions. If you got another problem please ask in our forum.

YAML error on first start

You will see this error if there is already a different version of ruamel.yaml installed on your system:

pkg_resources.VersionConflict: (ruamel.yaml 0.15.37 (c:\users\robert\appdata\local\programs\python\python36\lib\site-packages), Requirement.parse('ruamel.yaml<0.11,>=0.10')

This could have happened if you are upgrading to a newer version of MPF or you have incompatible versions of MPF, MPF-MC and/or the MPF-Monitor installed. The required ruamel.yaml version is different on newer MPF versions. We used to install ruamel 0.11 and switched to 0.15 in MPF 0.53+. MPF cannot start with two yaml libraries. To fix this check your versions pip3 list and check mpf, mpf-mc and mpf-monitor. Remove the wrong version and install the right one. All versions need to match (for instance all or all dev).

The following command will remove all three and install the latest release:

pip3 uninstall mpf mpf-mc mpf-monitor
pip3 install mpf mpf-mc mpf-monitor

This error can also occur if you already have ruamel.yaml installed in your python system packages for a non-MPF package. Often times, you will have a newer version of ruamel.yaml than MPF requires. Unfortunately, MPF cannot use a newer version of this package because that caused issues in the past because newer versions dropped support (wheels for windows) for older python versions. In the case that you need a different version than the one MPF requires, it is advised to create a python virtual environment and install the required packages there, and use that virtual environment for running MPF.

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