A Quick Guide to Getting Started with PyQGIS on Windows

Getting started with Python and QGIS can be a bit overwhelming. In this post we give you a quick start to get you up and running and maybe make your PyQGIS life a little easier.

There are likely many ways to setup a working PyQGIS development environment—this one works pretty well.

Requirements
Installing
- OSGeo4W
  - Setting the Environment
- Python Packages
Working on the Command Line
IDE Example
Workflow
- Creating a New Plugin
- Working with Existing Plugin Code
Troubleshooting

Requirements

OSGeo4W Advanced Install of QGIS
pip (for installing/managing Python packages)
pb_tool (cross-platform tool for compiling/deploying/distributing QGIS plugin)
A customized startup script to set the environment (pyqgis.cmd)
IDE (optional)
Vim (just kidding)

We’ll start with the installs.

Installing

Almost everything we need can be installed using the OSGeo4W installer available on the QGIS website.

OSGeo4W

From the QGIS website, download the appropriate network installer (32 or 64 bit)

Run the installer and choose the Advanced Install option
Install from Internet
Choose a directory for the install—I prefer a path without spaces such as C:\OSGeo4W
Accept default for local package directory and Start menu name
Tweak network connection option if needed on the Select Your Internet Connection screen
Accept default download site location
From the Select packages screen, select the following for installation:
- Desktop -> qgis: QGIS Desktop
- Libs -> qt4-devel (needed for lrelease/translations)
- Libs -> setuptools (needed for installing pip)

When you click Next a bunch of additional packages will be suggested—just accept them and continue the install.

Once complete you will have a functioning QGIS install along with the other parts we need. If you want to work with the nightly build of QGIS, choose Desktop -> qgis-dev instead.

If you’ve already installed QGIS using the OSGeo4W installer, just install the qt4-devel and setutools packages. If you installed QGIS using the standalone installer, the easiest option is to remove it and install from OSGeo4W. You can run both the standalone and OSGeo4W versions on the same machine, but you need to be extra careful not to mix up the environment.

Setting the Environment

To continue with the setup, we need to set the environment by creating a .cmd script. The following is adapted from several sources, and trimmed down to the minimum. Copy and paste it into a file named pyqgis.cmd and save it to a convenient location (like your HOME directory).


  @echo off
  SET OSGEO4W_ROOT=C:\OSGeo4W
  call "%OSGEO4W_ROOT%"\bin\o4w_env.bat
  call "%OSGEO4W_ROOT%"\apps\grass\grass-6.4.3\etc\env.bat
  @echo off
  path %PATH%;%OSGEO4W_ROOT%\apps\qgis\bin
  path %PATH%;%OSGEO4W_ROOT%\apps\grass\grass-6.4.3\lib

  set PYTHONPATH=%PYTHONPATH%;%OSGEO4W_ROOT%\apps\qgis\python;
  set PYTHONPATH=%PYTHONPATH%;%OSGEO4W_ROOT%\apps\Python27\Lib\site-packages
  set QGIS_PREFIX_PATH=%OSGEO4W_ROOT%\apps\qgis
  set PATH=C:\Program Files (x86)\Git\cmd;C:\Program Files (x86)\Vim\vim74;%PATH%
  cd %HOMEPATH%\development
  cmd.exe

You should customize the set PATH statement to add any paths you want available when working from the command line. I added paths to my git and vim installs.

The cd %HOMEPATH%\development statement starts the shell in my normal working directory—customize or remove as you see fit.

The last line starts a cmd shell with the settings specified above it. We’ll see an example of starting an IDE in a bit.

You can test to make sure all is well by double-clicking on our pyqgis.cmd script, then starting Python and attempting to import one of the QGIS modules:

 C:\Users\gsherman\development>python
 Python 2.7.5 (default, May 15 2013, 22:44:16) [MSC v.1500 64 bit (AMD64)] on win
 32
 Type "help", "copyright", "credits" or "license" for more information.
 >>> import qgis.core
 >>>

If you don’t get any complaints on import, things are looking good.

Python Packages

We need a couple of Python packages as well.

pip

There are several ways to install pip, but since we installed setuptools we can use easy_install:


    easy_install pip

Make sure to issue this command from your customized shell (double-click on pyqgis.cmd to start it).

pb_tool

With pip installed we can use it to install pb_tool:


    pip install pb_tool

More information on using pb_tool is available on the [project website.] [pb_tool website]

Working on the Command Line

Just double-click on your pyqgis.cmd script from the Explorer or a desktop shortcut to start a cmd shell. From here you can use Python interactively and also use pb_tool to compile and deploy your plugin for testing.

IDE Example

With slight modification, we can start our IDE with the proper settings to recognize the QGIS libraries:


    @echo off
    SET OSGEO4W_ROOT=C:\OSGeo4W
    call "%OSGEO4W_ROOT%"\bin\o4w_env.bat
    call "%OSGEO4W_ROOT%"\apps\grass\grass-6.4.3\etc\env.bat
    @echo off
    path %PATH%;%OSGEO4W_ROOT%\apps\qgis\bin
    path %PATH%;%OSGEO4W_ROOT%\apps\grass\grass-6.4.3\lib

    set PYTHONPATH=%PYTHONPATH%;%OSGEO4W_ROOT%\apps\qgis\python;
    set PYTHONPATH=%PYTHONPATH%;%OSGEO4W_ROOT%\apps\Python27\Lib\site-packages
    set QGIS_PREFIX_PATH=%OSGEO4W_ROOT%\apps\qgis
    set PATH=C:\Program Files (x86)\Git\cmd;C:\Program Files (x86)\Vim\vim74;%PATH%
    cd %HOMEPATH%\development
    start "PyCharm aware of Quantum GIS" /B "C:\Program Files (x86)\JetBrains\PyCharm 3.4.1\bin\pycharm.exe" %*

We only changed the last line, adding the start statement with the path to the IDE (PyCharm). If you save this to something like pycharm.cmd, you can double-click on it to start PyCharm. The same method works for other IDEs, such as PyDev.

Within your IDE settings, point it to use the Python interpreter included with OSGeo4W—typically at: %OSGEO4W_ROOT%\bin\python.exe. This will make it pick up all the QGIS goodies needed for development, completion, and debugging. In my case OSGEO4W_ROOT is C:\OSGeo4W, so in the IDE, the path to the correct Python interpreter would be: C:\OSGeo4W\bin\python.exe.

Make sure you adjust the paths in your .cmd scripts to match your system and software locations.

Workflow

Here is an example of a workflow you can use once you’re setup for development.

Creating a New Plugin

Use the Plugin Builder plugin to create a starting point [1]
Start your pyqgis.cmd shell
Use pb_tool to compile and deploy the plugin (pb_tool deploy will do it all in one pass)
Activate it in QGIS and test it out
Add code, deploy, test, repeat

Working with Existing Plugin Code

The steps are basically the same was creating a new plugin, except we start by using pb_tool to create a new config file:

Start your pyqgis.cmd shell
Change to the directory containing your plugin code
Use pb_tool create to create a config file
Edit pb_tool.cfg to adjust/add things create may have missed
Start at step 3 in Creating a New Plugin and press on

Troubleshooting

Assuming you have things properly installed, trouble usually stems from an incorrect environment.

Make sure QGIS runs and the Python console is available and working
Check all the paths in your pygis.cmd or your custom IDE cmd script
Make sure your IDE is using the Python interpreter that comes with OSGeo4W

[pb_tool website]: http://g-sherman.github.io/plugin_build_tool

[1] Plugin Builder 2.6 will support generation of a pb_tool config file

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