I’m starting off slow, so today we’ll add a marker with some extra features. Since the map from yesterday is already centered on the big earthquake, lets add a marker there. Adding a Marker To create a marker, Leaflet uses the L.marker class: var earthquakeMarker = L.marker([61.346, -149.955]); This creates the marker, but it needs to be added to the map: earthquakeMarker.addTo(map); This gives us: Good so far, but looking at the map tells us nothing about the marker.
Background We at Locate Press have been working on a new book: Leaflet Cookbook, by Numa Gremling. The book is chock-full of over 300 pages of recipes and information to get the most of your web maps. The book is content complete and available as a preview. I’ve dabbled in Leaflet in the past, but only scratched the surface. So, I’ve decided to spend two weeks starting from the ground up and create a decent web map.
We’ve released version 3.1 of the Plugin Builder for QGIS 3.x. This version contains a number of bug fixes and performance enhancements. Here are some of the changes included since version 3.0.3: Fix issue with reload on generated plugins Move dialog creation to run method to improve startup performance Move help file generation files to proper method Include missing tags file Attempt to compile resources.qrc when plugin is generated (requires pyrcc5 in path) Set deployment directory in Makefile based on user OS (pb_tool is recommended over make) Check for valid URL format for tracker and repository Compiling Resource File If you have the resource compiler pyrcc5 in your path, the resource file will be compiled automatically when you generate your new plugin.
There’s been several posts to GIS StackExchange along the lines of: Where’s my .qgis3 folder? Prior to QGIS 3, the .qgis/.qgis2 folder was found under your home directory. At version 3, the folder has moved to a more standard profile location for your operating system. There are a couple of ways to determine where the folder is located: Use the Settings->User Profiles->Open active profile folder menu item Use QgsApplication.qgisSettingsDirPath from Python or the console Here are the “standard” locations for Linux, Mac, and Windows, as found under your HOME directory:
Getting started with Python and QGIS 3 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. Contents Requirements Installing OSGeo4W Setting the Environment pb_tool Working on the Command Line IDE Example Workflow Creating a New Plugin Working with Existing Plugin Code Troubleshooting
QGIS data providers are written in C++, however it is possible to simulate a data provider in Python using a memory layer and some code to interface with your data. Why would you want to do this? Typically you should use the QGIS data providers, but here are some reasons why you may want to give it a go: There is no QGIS data provider The generic access available through OGR doesn’t provide all the features you need You have no desire to write a provider in C++ No one will write a C++ provider for you, for any amount of money If you go this route you are essentially creating a bridge that connects QGIS and your data store, be it flat file, database, or some other binary format.
This minor update to the Plugin Builder allows you to choose where your plugin menu will be located. Previously your menu was placed under the Plugins menu. At version 2.8.1 you can choose from the following main menu locations: Plugins Database Raster Vector Web Plugins is the default choice when you open Plugin Builder. The value you choose is also written to the category field in your metadata.txt file.
Plugin Builder 2.8 is now available. This is a minor update that adds: Suggestion for setting up an issue tracker and creating a code repository Suggestion for a home page Tag selection from a list of current tags Documentation update, including information about using pb_tool to compile, deploy, and package your plugin New URLs for Plugin Builder’s home page and bug tracking Optional is now Recommended In previous versions the following items were “Optional” when creating a new plugin:
Here is a short list of resources available when writing Python code in QGIS. If you know of others, please leave a comment. Blogs/Websites In alphabetical order: GIS StackExchange Kartoza Linfiniti Lutra Consulting Nathan Woodrow Nyall Dawson Twitter #pyqgis Documentation Choose the version to match your QGIS install PyQGIS Cookbook QGIS API Example Code Existing plugins can be a great learning tool Code Snippets in the PyQGIS Cookbook Plugins/Tools Script Runner: Run scripts to automate QGIS tasks Plugin Builder: Create a starter plugin that you can customize to complete your own plugin Plugin Reloader: Allows you to reload a plugin from within QGIS pb_tool: Tool to compile and deploy your plugins Books PyQGIS Programmers Guide Geospatial Desktop: GIS Scripting (PDF)
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. Contents 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
The Plugin Builder is a great tool for generating a working plugin project that you can customize. One of the main tasks in the development cycle is deploying the plugin to the QGIS plugin directory for testing. Plugin Builder comes with a Makefile that can be used on Linux and OS X to aid in development. Depending on your configuration, the Makefile may work on Windows. To help in managing development of your projects, we’ve come up with another option—a Python tool called pb_tool, which works anywhere QGIS runs.
If you’re a developer, or have looked at the QGIS source code, you’ve likely noticed that most C++ classes in the project start with Qgs. Back before the dark ages of QGIS, Trolltech (now Digia) allowed you to reserve name prefixes for classes that used the Qt framework. Shortly afterwards, I reserved the gs prefix for my use, resulting in class names that start with Qgs. You might think this is based on some mangling of words like QGIS or perhaps GIS, but it was purely egocentric:
The PyQGIS Programmer’s Guide is now available in both paperback and PDF. A sample chapter is also available for download. The book is fully compatible with the QGIS 2.x series of releases. See locatepress.com for details.
The preview release of the PyQGIS Programmer’s Guide is now available for purchase from Locate Press.
We’re planning a couple of training classes for March: Introduction to QGIS Extending QGIS with Python Each is a one day class and we plan to run them back to back. If you are local or just want to come to Alaska in March for some spring skiing, northern lights viewing, or to experience the equinox, please hop over to GeoApt and let us know so we can plan accordingly.