Graphics Reference
In-Depth Information
Summary
In this chapter, we explored the QGIS Python Console, and how to use it for a variety of
programming tasks. We also used the console to delve more deeply into the QGIS Python
programming environment.
As we worked through this chapter, we learned what the various toolbar buttons and con-
trols do within the QGIS Console, and how to enter commands using the Python Shell. We
looked at how we can use the Python Interpreter Log to view the previous output and re-
enter commands you executed earlier. We saw the ways in which you can use autocomple-
tion to enter your Python code more quickly, and also learned about the parameters that the
various PyQGIS functions and methods accept.
We then looked at how to enter and execute Python scripts using the built-in source code
editor. We discovered that the Python Console is itself written in Python, allowing you to
explore the source code and manipulate the console itself using the Python code.
We learned how to create a startup script that is run automatically whenever QGIS starts
up, and how you can use this to set up the console to open automatically and prevent it
from acting as a dockable window.
Next, we examined the process of loading geospatial data directly using your Python
scripts, without first having to load it into a QGIS map layer. We saw how to identify the
attributes defined by a shapefile, how to scan through the features within a shapefile, and
the ways in which the PyQGIS libraries allow you to perform common geospatial calcula-
tions.
We then looked at the various ways in which you can make use of QGIS user interface ele-
ments within your Python scripts, including the status bar, message bars, progress indicat-
ors, and the QGIS message log.
Finally, we saw how you can use standard PyQt classes to create your own windows and
dialog boxes to provide a sophisticated user interface for your Python scripts.
In the following chapter, we will work more directly with the QGIS Python libraries, learn-
ing how these libraries are structured and how you can use them to perform various sorts of
geospatial data manipulation and display the results on a map.
