From Slicer Wiki
Jump to: navigation, search
Home < Documentation < 4.4 < Extensions < PyDevRemoteDebug

For the latest Slicer documentation, visit the 4.10 page.

Introduction and Acknowledgements

Author: Andras Lasso (PerkLab, Queen's University)
Contact: Andras Lasso, <email></email>
Project website:
License: Slicer license


Extension Description


Python Debugger is an extension of 3D Slicer to allow debugging of Python scripts in the Eclipse integrated development environment using PyDev.

Visual debugging (setting breakpoints, execute code step-by-step, view variables, stack, etc.) of Python scripted module is possible by using PyDev.


  • Python debugger (in the module list: Developer Tools)

Use Cases



  • Install PyDev: the simplest is to use the standalone LiClipse package
  • Run PyDev and enable the remote debugger tool (if you have trouble following these steps then you can find detailed instructions here):
    • Enable PyDev server: in the menu Window > Customize perspective > Command groups availability > PyDev debug
    • Open the debug window: in the menu Window > Open Perspective > Other > Debug
  • In Slicer:
  • Install the Python debugger extension
    • Open the Python debugger module (in Developer Tools category)
    • In the Settings section set the directory that contains the file. Usually it is in the Eclipse plugins directory /...pydev.../pysrc.

Start debugging

  • In PyDev
    • Start the server: on the toolbar click the button "PyDev: start the pydev server"


  • In Slicer:
    • Open the Python debugger module (in Developer Tools category)
    • Click on Connect
    • If the debugger is successfully attached, then it will pause Slicer, so Slicer becomes unresponsive (until its execution is resumed in PyDev)
  • In PyDev.
    • Slicer execution is now paused. Resume Slicer execution by pressing the "Resume" button on the toolbar.
    • Load your .py file into PyDev and add breakpoints (Ctrl+Shift+B) where you want your execution to stop for debugging.
    • Important: you can open a terminal, where you can enter Python commands while the execution is paused (you have access to all Slicer variable, it has auto-complete, etc.) by clicking on "Open Console" (small button at the top of the console view) then chose "PyDev Console" and then "PyDev Debug Console" (after this the title of the console should be "PyDev Debug Console" instead of the default "Debug Server").

Information for Developers