The Python console
API Note: Any QGIS APIs referenced will link out to the Python API Docs.
Exploring the console
The Python Console and Python script editor is a great way to explore the QGIS api in order to try out the logic of your code before adding it to you scripts.
We won't spend long in here, just enough to try out some basic QGIS APIs and get used to the UI.
Exercise: Using the console
Open the console using
Plugins -> Python Console
Inside the console we can run any commands we want to try. This is a full interactive Python console so any python code will work here.
Exercise: First Python commands
Try something basic like the following and hit enter
The output is:
Exercise: First PyQGIS commands
Lets try some QGIS commands. Try each one and check the results
QGIS exposes a object called
This object exposes methods that you can use to make some more complex operations easier. It's a wrapper around some of
the lower level object. One example is
Exercise: New project from PyQGIS
Run the following command to create a new project
Exercise: Access the main canvas
We can access the main canvas and it's scale function from here.
Lets move on the the script editor
The script editor
From inside the console we can open the script editor. This editor can be used to write more complex scripts where the console is normally only used for smaller one off logic.
Exercise: Opening the editor
Open the editor from inside the Python Console using the following button and the script editor will open on the left.
For a quick test we can write the a simple one line command and run the script
Exercise: Running the first commands
Tip: Run selected text
You can run just the selected text as well with
Ctrl+E if you have a more complex script and need to check
just parts of it.
Lower case all layer names
For this example we will create a new file using the plus button and write a script to lower case all the layer names in the project.
Exercise: Import QGIS modules
Although QGIS has auto imported all the QGIS APIs into the console it's good practice to import them in your scripts to make things clear
In the new script add the following at the top
from qgis.core import QgsProject
Now we are ready to loop over all the layers and rename them to lower case. Copy the following into the script editor and use the green edit button to run the script
Exercise: Upper case all layer names
for layer in QgsProject.instance().mapLayers().values(): print(layer.name()) layer.setName(layer.name().upper()) print("New name", layer.name())
The full script should look like this:
from qgis.core import QgsProject for layer in QgsProject.instance().mapLayers().values(): print(layer.name()) layer.setName(layer.name().upper()) print("New name", layer.name())
The output in the console should be
and the layers panel with the new names