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Plugins are a great way to extend the functionality of QGIS. You can write plugins using Python that can range from adding a simple button to sohpisticated toolkits. This tutorial will outline the process involved in setting up your development environment, designing the user interface for a plugin and writing code to interact with QGIS. Please review the Getting Started With Python Programming (QGIS3) tutorial to get familiar with the basics.

Note

If you are building a new plugin, I strongly recommend building a Processing Plugin instead of the GUI plugin described in this tutorial. See Building a Processing Plugin (QGIS3) for details.

Overview of the Task¶

We will develop a simple plugin called SaveAttributes that will allow users to pick a vector layer and write its attributes to a CSV file.

Get the Tools¶

Qt Creator¶

Qt is a software development framework that is used to develop applications that run on Windows, Mac, Linux as well as various mobile operating systems. QGIS itself is written using the Qt framework. For plugin development, we will use an application called Qt Creator to design the interface for our plugin.

Download and install the Qt Creator installer from Qt Offline Installers. Make sure you select Qt Creator on the download page. Note that you will have to create a free Qt account to install the package.

Note

OSGeo4w installer for QGIS on Windows include a copy of Qt Designer program which is a lightweight version of Qt Creator and perfectly suitable for building plugins. You may skip downloading Qt Creator and use it instead from C:OSGeo4W64binqgis-designer.

Python Bindings for Qt¶

Since we are developing the plugin in Python, we need to install the pythonbindings for Qt. The method for installing these will depend on the platformyou are using. For building plugins we need the pyrcc5 command-line tool.

Windows

Relevant pyhon bindings are included in the QGIS install on Windows. But to use them from the plugin folder, we need to indicate the path to the QGIS install.

Create a Windows Batch file (.bat extension) with the following content and save it on your computer as compile.bat. We will later copy this file to the plugin folder. If you installed QGIS at a different path, replace the C:OSGeo4W64bin with your path.

Mac

Install the Homebrew package manager. Install PyQt package by running the following command:

Linux

How To Install Qt Platform Plugin Windows 10

Depending on your distribution, find and install the python-qt5 package. On Ubuntu and Debian-based distributions, you can run the following command:

Note

You may find that QGIS has already installed this package.

A Text Editor or a Python IDE¶

Any kind of software development requires a good text editor. If you already have a favorite text editor or an IDE (Integrated Development Environment), you may use it for this tutorial. Otherwise, each platform offers a wide variety of free or paid options for text editors. Choose the one that fits your needs.

This tutorial uses Notepad++ editor on Windows.

Windows

Notepad++ is a good free editor for windows.Download and install the Notepad++ editor.

Note

If you are using Notepad++, makes sure to go to Settings ‣ Preferences ‣ Tab Settings and enable Replace by space. Python is very sensitive about whitespace and this setting will ensure tabs and spaces are treated properly.

Plugin Builder plugin¶

There is a helpful QGIS plugin named PluginBuilder which creates all the necessary files and the boilerplate code for a plugin. Find and install the PluginBuilder plugin. See Using Plugins for more details on how to install plugins.

Plugins Reloader plugin¶

This is another helper plugin which allows iterative development of plugins. Using this plugin, you can change your plugin code and have it reflected in QGIS without having to restart QGIS every time. Find and install the PluginReloader plugin. See Using Plugins for more details on how to install plugins.

Note

Plugin Reloader is an experimental plugin. Make sure you have checked Show also experimental plugins in Plugin Manager settings if you cannot find it.

Procedure¶

Open QGIS. Go to Plugins ‣ Plugin Builder ‣ Plugin Builder.

You will see the QGIS Plugin Builder dialog with a form. You can fill the form with details relating to our plugin. The Class name will be the name of the Python Class containing the logic of the plugin. This will also be the name of the folder containing all the plugin files. Enter SaveAttributes as the class name. The Plugin name is the name under which your plugin will appear in the Plugin Manager. Enter the name as SaveAttributes. Add a description in the Description field. The Module name will be the name of the main python file for the plugin. Enter it as save_attributes. Leave the version numbers as they are and enter your name and email address in the appropriate fields. Click Next.

Enter a brief description of the plugin for the About dialog and click Next.

How To Install Qt Platform Plugin Windows 10

Select the Toolbuttonwithdialog from the Template selector`. The Text for menu item value will be how the users will find your plugin in QGIS menu. Enter it as SaveAttributesasCSV. The Menu field will decide where your plugin item is added in QGIS. Since our plugin is for vector data, select Vector. Click Next.

Plugin builder will prompt you for the type of files to generate. Keep the default selection and click Next.

As we do not intend to publish the plugin, you may leave the Bug tracker, Repository and Home page values to default. Check the Flag the plugin as experimental box at the bottom and click Next.

You will be prompted to choose a directory for your plugin. For now, save it to a directory you can locate easily on your computer and click Generate.

Ost2pst serial key. Next, press the generate button. You will see a confirmation dialog once your plugin template is created.

Note

You may get a prompt saying that pyrcc5 is not found in the path. You can ignore this message.

Before we can use the newly created plugin, we need to compile the resources.qrc file that was created by Plugin Builder. This file is part of the Qt Resource System which references all binary files used in the plugin. For this plugin, it will only have the plugin icon. Compiling this file generates application code that can be used in the plugin independent which platform the plugin is being run. Follow the platform specific instruction for this step.

Windows

You can now copy the