In this recipe, we will configure Eclipse to debug QGIS Python scripts.
Both QGIS and Eclipse must be configured for debugging so that the two pieces of software can communicate. Eclipse attaches itself to QGIS in order to give you insights into the Python scripts running in QGIS. This approach allows you to run scripts in a controlled way that can pause execution while you monitor the program to catch bugs as they occur.
The following steps will add two plugins to QGIS, which allows Eclipse to communicate with QGIS. One plugin, Plugin Reloader, allows you to reload a QGIS plugin into memory without restarting QGIS for faster testing. The second plugin, Remote Debug, connects QGIS to Eclipse.
Remote Debug is an experimental plugin, so you must ensure that experimental plugins are visible to the QGIS plugin manager in the list of available plugins.
Now that QGIS is configured for debugging in Eclipse, we will configure Eclipse to complete the debugging communication loop, as shown in the following steps:
HelloWorldPlugin
folder, as shown in the following screenshot:The previous parts of this recipe configured Eclipse and QGIS to work together in order to debug QGIS plugins. In this section, we will test the configuration using the simplest possible plugin, HelloWorld, to run Eclipse using the Debug Perspective. We will set up a break point in the plugin to pause the execution and then monitor plugin execution from within Eclipse, as follows:
HelloWorld
folder, open the file HelloWorld.py
.hello_world()
function and double-click on the left-hand side of the line number to set a break point, which is displayed as a green-icon:Debug Server at port: 5678
Python Debugging Active
hello_world()
function is highlighted at the break point.The RemoteDebug plugin acts as a client to the PyDev debug server in order to send the Python script's execution status from QGIS to Eclipse. While it has been around for several versions of QGIS now, it is still considered experimental.
The PluginReloader plugin can reset plugins that maintain state as they run. The HelloWorld plugin is so simple that reloading is not needed to test it repeatedly. However, as you debug more complex plugins, you will need to run it in order to reset it before each test. This method is far more efficient and easier to use than closing QGIS, editing the plugin code, and then restarting.
You can find out more about debugging QGIS, including using other IDEs, at http://docs.qgis.org/2.6/en/docs/pyqgis_developer_cookbook/ide_debugging.html.