Using PyCharm with Workbench

Developing and debugging with PyCharm on Windows

The first thing that needs to be done is creating the PyCharm project and configuring the project settings. Please follow the instructions at Setting up PyCharm on Windows.

After the project settings have been configured, a Run/Debug configuration needs to be created. To edit the configurations go to Run->Run... and select Edit Configurations. Select Templates->Python, and hit the green + in the top left. The necessary changes to the configuration are:

  • Select the Mantid Python interpreter that was added to the project in the instructions above. Do not use the default interpreter on Windows.
  • Set up Script Path and Working Directory as follows:
Paths for running a Debug build:
  • Set the Script Path to <Mantid Build Directory>/bin/Debug/workbench-script.pyw
  • Set the Working Directory to <Mantid Build Directory>/bin/Debug
Paths for running a Release build:
  • Set the Script Path to <Mantid Build Directory>/bin/Release/workbench-script.pyw
  • Set the Working Directory to <Mantid Build Directory>/bin/Release

Note that the only difference here is the change from /bin/Debug/ to /bin/Release/.

Make sure you have finished the build you are using (Debug or Release), or there will be import errors.

Common errors

qtpy.PythonQtError: No Qt bindings could be found

<Mantid Source Directory>/external/src/ThirdParty/lib/qt5/bin is missing from the Path environment variable.

ImportError: DLL load failed: The specified module could not be found.

<Mantid Source Directory>/external/src/ThirdParty/lib/qt5/lib is missing from the Path environment variable.

The fix for these errors is to make sure you have started PyCharm through the <Mantid Build Directory>/pycharm.bat script. This sets up the PATH variable for the Python imports.

Additionally, check that your PyCharm Run/Debug configuration does not overwrite the PATH variable. To check go to Edit Configurations -> Environment Variables and click the folder icon on the right side. In the Name column there should not be a Path variable. If there is one, try deleting it and running your configuration again.

Identifying issues with PyCharm configuration

Follow these steps to narrow down the root of potential errors:

  • Go to the Mantid Build Directory
  • Start command_prompt.bat. If the command_prompt.bat file is missing, the build has not been fully generated from CMake or is corrupted.
  • In the command prompt open the Python interpreter with python.
  • Try to import the package where the error is happening. For example if there is an error on import qtpy, from PyQt5 import QtCore, try running that line in the interpreter.
  • If the import succeeds, then there is a problem with the PATH configuration in PyCharm.
  • If the import fails, then it is possible that Mantid has not been fully built. If you are trying to import PyQt4/PyQt5/qtpy, and it fails to import from the command prompt, then the external dependencies might not be downloaded or are corrupted.

Running other Mantid widgets in PyCharm

The widgets in mantidqt/widgets can be run independently of the Workbench. They still need the relevant PATHs available - to load the mantid, mantidqt, and various other libraries.

The easiest way to do this is to set the script path to the widget’s startup script, but leave the working directory to point at <Mantid Build Directory>/bin/Debug or <Mantid Build Directory>/bin/Release

For example to run the MatrixWorkspaceDisplay:

  1. Copy your default configuration (the copy icon on the top left of the configuration window).
  2. Set the Script Path to <Mantid Source Dir>/qt/python/mantidqt/widgets/matrixworkspaceviewer. This package has a file which makes it runnable.
  3. You might have to CHANGE back the working directory to <Mantid Build Dir>/bin/Debug.
  4. Click OK, then running the configration should start the MatrixWorkspaceDisplay.