15.1. VisIt’s Python Command Line via the Command Window


Fig. 15.1 Command Window

It is possible for VisIt’s GUI and Python Interface to share the same viewer component at runtime. When you invoke visit at the command line, VisIt’s GUI is launched. When you invoke visit -cli at the command line, VisIt’s CLI (Python interface) is launched. If you want to use both components simultaneously then you can use VisIt’s Command Window . The Command Window can be opened by clicking on the Command menu option from the Controls menu. The Command Window consists of a set of eight tabs in which you can type Python scripts. When you type a Python script into one of the tabs, you can then click the tab’s Execute button to make VisIt try and interpret your Python code. If VisIt detects that it has no Python interpreting service available, it will launch the CLI (connected to the same viewer component) and then tell the CLI to execute your Python code. Note that the Command Window is just for editing Python scripts. Any output that results from the Python code’s execution will be displayed in the CLI program window (see Figure 15.1).

15.1.1. Saving the Command Window’s Python scripts

The Command Window is meant to be a sandbox for experimenting with small Python scripts that help you visualize your data. You will often hit upon small scripts that can be used over and over. The scripts in each of the eight tabs in the Command Window can be saved for future VisIt sessions if you save your settings. Once you save your settings, any Python scripts that are present in the Command Window are preserved for future use.

15.1.2. Clearing a Python script from a tab

If a Python script in one of the Command Window’s tabs is no longer useful then you can click that tab’s Clear button to clear out the contents of the tab so you can begin creating a new script in that tab. If you want VisIt to permanently delete the script from the tab then you must save your settings after clicking the Clear 3button.

15.1.3. Using the GUI and CLI to design a script

Writing a Python script that performs visualization from scratch can be difficult. The process of setting up a complex visualization can be simplified by using both the GUI and the CLI at the same time. For example, you can use VisIt’s GUI to set up the plots that you initially want to visualize and then you can save out a session file that captures that setup. Next, you can open a text editor and create a new Python script. The first line of your Python script can use VisIt’s RestoreSession command to restore the session file that you set up with the GUI from within the Python scripting environment. For more information on functions and objects available in VisIt’s Python interface, see the VisIt_ Python Interface manual. After using the RestoreSession function to set VisIt situated with all of the right plots, you can proceed with more advanced Python scripting to alter the view or move slice planes, etc. Once you have completed your Python script in a text editor, you can pasted it into the Command Window to test it or you can pass it along to VisIt’s command line movie tools to make a movie.