Understanding the QGIS plugin architecture

As we saw in Chapter 1, Getting Started with QGIS, QGIS plugins are stored as Python packages in the ~/.qgis2/python/plugins directory.

Tip

Depending on your operating system and the version of QGIS you're using, the .qgis2 directory might be named .qgis.

The plugin's package includes a number of Python modules and other files. At a minimum, the plugin package must include:

• __init__.py: This is a package initialization module that contains the class factory function, which creates and initializes the plugin.
• metadata.txt: This is a text file that contains information about the plugin, including the plugin's version number, the name of the plugin, and the plugin's author.

In addition, most plugins will include:

• A separate Python module that contains a class definition for the plugin. The plugin class implements a number of specially named methods that get called to start up and shut down the plugin.
• One or more user-interface template...