Variable Inspector

Description and main features

The Variable Inspector extension, which currently supports python and R kernels, enables to collect all defined variables and display them in a floating window. The window not only display the name of variables but also their type, size in memory and content. The columns are sortable. The window is draggable, resizable, collapsable. The list of displayed variables is automatically updated at each cell execution. Variables can be deleted from workspace by clicking a link. Position and state (displayed/collapsed) are stored in the notebook’s metadata and restored at startup.

The extension supports multiple kernels. To add support for a new kernel, one has to

  • provide a library which loads required modules and define a function which lists all variables, together with their name, type, size and content. The output of this function must be a JSON representation of a list of objects (one for each variable) with keys ‘varName’,’varType’, ‘varSize’, ‘varContent’,
  • provide the command for deleting a variable, as delete_cmd_prefix and delete_cmd_postfix, eg. for rm(variable), specify rm( and ).
  • give the command to refresh the list of variables (usually this is a call to the function defined in the library above). This information can be provided either in the source file or in the yaml config file.

In any case, contributions to support further kernels will be very welcome!



The initial configuration can be given using the IPython-contrib nbextensions facility. It includes:

  • varInspector.window_display - Display at startup or not (default: false)
  • varInspector.cols.lenName: (and .lenType, .lenVar) - Width of columns (actually the max number of character to display in each column)
  • varInspector.kernels_config - json object defining the kernels specific code and commands.


  • The displayed size of variables use the getsizeof() python method. This method doesn’t work for all types, so the reported size is to be considered with some caution. The extension includes some code to correctly return the size of numpy arrays, pandas Series and DataFrame but the size for some other types may be incorrect.
  • The extension builds on some example code provided by the ipywidgets package (essentially the _fill method).
  • The extension uses Christian Bach’s table sorter jquery plugin. License file is included.


  • @jfbercher march 22, 2017 – initial release
  • @jfbercher april 03, 2017 – multiple kernel support. added support for R kernels.