VSCRIPT: A scripting language extension for VISTA

INTRODUCTION TO SCRIPTING:

Graphical User Interface's (GUI's) are excellent as an introduction to doing a task. This helps to get one initiated but when one starts doing complicated, conditional-based, repititive tasks, GUI's either cannot do them or it is extremely time-consuming and tedious to do so.

Scripting is the process of writing small scripts ( 1-2 pages long ) which do a simple task. Scripting is not limited to command line but can also manipulate or create graphical components such as plots. Scripting automates tasks and makes them repeatable. This makes the work done by an individual easily transferrable to future persons who encounter similar tasks. This helps create a body of reusable code with more ease than traditional programming.

Furthermore scripting is interactive, ie. users can try out various commands like the ones above by typing them line by line on the command interpreter or pasting the entire set of lines at the interpreter. The interpreter then executes those lines and waits for further commands. This is again of great use as one can experiment with various scenarios and then write those that worked into a script file for reuse.

Scripting could be used for :-

a tool for model/data comparisions
a tool for model/model incremental analysis
a tool for dynamic documentation
a tool for checking model run sanity
a tool for automated data quality checking/flag setting with rules

INTRODUCTION TO VSCRIPT:

VISTA (VISualization Tool and Analyzer) is a GUI that was developed by DWR. VISTA was described in the June 1998 Annual Report. The purpose of VISTA is to provide time-series data retrieval, management, manipulation and visualization.

VSCRIPT is a scripting language extension for VISTA. It allows a user to write simple scripts using VISTA's functionality. VSCRIPT is now an integral part of VISTA's distribution.

The underlying language of VSCRIPT is Python. This a mature and stable scripting language which is very close in syntax to the underlying language of VISTA ( i.e. Java). VSCRIPT is an extension based on JPython.

Python is well documented and has a large user community. JPython taps into the power and libraries of two languages Java and Python to give the user desired flexibility and power.

A inhouse class was given in getting started with VSCRIPT. It is available here.

FUTURE DIRECTIONS

Documentation:
There are a number of modules available in VISTA to manipulate and display data. In order to use this functionality the user needs to be informed. For this purpose there will be VSCRIPT classes in the future. Furthermore documentation of sample scripts and VISTA functionality will be improved.
Library of scripts for common tasks
Certain data processing tasks are repeated by users in the course of doing various studies. The aim of scripting is to make them repeatable. Furthermore if the task is generally useful enough it becomes useful enough to parametrize the script in terms of arguments required to do the task so that the script can be customized by future users faced with similar tasks. A scripting library for commonly used scripts will be documented and expanded upon in the future.