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In this tutorial, we’ll walk through how to create a shapefile from scratch with the QGIS Python (PyQGIS) API. You shouldn’t need to do this, but if you’re running into problems where functions don’t show up you can import the qgis module at the beginning. This usually isn’t a problem but there have been a…
With the PyQGIS API you are able to use Python in QGIS to automate the creation of map layouts. There are two reasons this is really awesome! First, once you’ve written the initial code to set up the map, you can change map symbology or map layers and exactly replicate layout. Second, once you have…
This tutorial will teach you how to render (print or save) a QGIS layer as an image using the PyQGIS Python API. Automating layer rendering can be very useful to create and save visualizations that have consistent styling, extent and format. The first thing you need to do is create a QImage. Here we create…
In a previous tutorial I showed you how to access raster values and data with the Geospatial Data Abstraction Library (GDAL). This tutorial will show you how to create a raster with GDAL. Start by importing the gdal and osr Python modules. The osr module is used for handling spatial references. Also import numpy. Now…
PyQGIS has some methods for accessing single values in a raster, but the best way to access raster data is using the Geospatial Data Abstraction Library, or GDAL. GDAL comes pre-installed on the QGIS Python interpreter, so if you access the Python interpreter from QGIS (Plugins > Python Console) you won’t have to install any…
Deleting features is a common operation in QGIS. It is easy to automate this task with Python, allowing you to quickly delete features based on any conditions you set. First, select the layer from which you want to delete features. This line of code will select the first layer with the name ‘layer name’. You…
Geometry is what defines the shape and spatial location of a feature. Features can be points, lines, or polygons, can be anywhere on earth, and can be represented by coordinates in a number of different units (depending on the coordinate reference system, or projection). Points are represented by a single coordinate pair while lines and…
The QGIS Python API (PyQGIS) makes it possible to automate creation of point features. This tutorial will show you how to add features to an existing shapefile. For this example we will assume the layer containing the point features is already opened in the QGIS table of contents. First, we save all layers with a…
It is tedious, and not practical, to manually type in values for array creation. In this tutorial we will go through methods for automating array creation and importing tabular data into numpy arrays. Creating empty arrays With numpy you don’t actually create an ‘empty’ array. But you can create an array without intializing specific values. This can be useful…
We’ve gone through the basics to manually create arrays of different dimensions and shapes. There will be times that you will want to query array shapes, or automatically reshape arrays. This tutorial will show you how to use numpy.shape and numpy.reshape to query and alter array shapes for 1D, 2D, and 3D arrays. Different methods are required to find…
Creating a simple array After numpy is installed, we can begin to create arrays. First, we’ll need to import numpy into our python project. Here I use the statement, import numpy as np, to limit my typing later. This code will allow me to use np in my script to represent instead of typing the full numpy everytime. Then, we can create a simpy…
Check Installation First, check to see if you already have numpy installed. From the terminal, you can use pip to do this. If numpy is installed you will get output similar to this. If numpy is not installed no output will be shown. Install numpy numpy can be installed simply using pip. Check version You can check the numpy version using pip show as demonstrated above. Video tutorial This…
Requirements: Python version 2.7 or greater Beginner skills with python Desire to learn numpy Objectives: Teach the basics of using numpy in python Provide data science applications of numpy Introduce advanced numpy concepts What is numpy? numpy is a powerful python package for handling arrays. It uses C libraries to optimize procedures that would otherwise be slow/computationally expensive in python. What can I do…
Objectives: Select features from a vector layer Iterate over selected features Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write…
Objectives: Retrieve data from the vector attribute table Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write code in the…
Objectives: Get statistics for a raster band Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write code in the editor…
Objectives: Get information from layers that have already been added to the QGIS interface Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I…
Objectives: Load raster and vector layers without adding them to the QGIS interface Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer…
Objectives: Query the value of a raster layer at a points Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write…
Objectives: Add fields to a shapefile Delete fields from a shapefile Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I prefer to write…
Objectives Load and symbolize a vector layer with pyqgis Apply basic and graduated symbology Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into the console, or select the pad and paper icon to write code in the editor. I…
More information can be found in the PyQGIS Developer Cookbook. Requirements QGIS version 3.0, or greater Objectives Load and symbolize a raster layer with pyqgis Get statistics from a raster band Open the QGIS Python Console From the menu, select Plugins -> Python Console, or Ctrl + Alt + P (Windows) You can type directly into…