PyQGIS – Activating Temporal Properties of Vector Layer Using PyQGIS

pyqgistemporal-controller

I'm trying to activate the dynamic temporal control on a vector layer with PyQGIS.

I have a function creating a line vector layer from a CSV, I am now trying either to set them as temporal (not temporary) ones during the creation of the layer, or once they are created. Also, I would like to set the configuration, by choosing the Unique Field for date and hour or Separate Field for starting and ending time

Here is my script which creates the layer I need :

class processing(object):
    def __init__(self , layer_name, data, collumn): #data = pandas dataframe
    start_time = time.time()

    self.layer_name = layer_name
    self.frame = data
    df = self.frame[self.frame['id'] == collumn]
    self.data = df.reset_index(drop=True)

    self.ListPointsQGS= [] #list of qgs points to be used later


    for index, row in self.data.iterrows():
        self.ListPointsQGS.append(QgsPoint(float(row['y']),float(row['x'])
        
    self.layer = iface.addVectorLayer("LineString?crs=epsg:4326&field=id:integer&index=yes",   layer_name ,"memory")


   
    self.feature = QgsFeature()      

    self.layer.startEditing()
    self.pr = self.layer.dataProvider()

    self.pr.addAttributes([  
                                QgsField("x",  QVariant.Double),
                                QgsField("y", QVariant.Double),
                                QgsField("date", QVariant.DateTime)])

This creates my layer, to be filled later with data.

I have tried using the QgsVectorLayerTemporalProperties class and the QgsTemporalProperty but I can't understand how to use them from the documentation.
I saw many different classes to create a vector layer and therefore replace the iface.addVectorLayer , some of which allowing building options, but none allowing to set it as a temporal layer.

At the end, my goal is to set up a user interface using the temporal control widget (which will use a column full of dates) in order to allow a user to see vector lines appearing one by one, without having to go in the proprities of all of them to check the box and turn them into temporal layer.

How could I achieve this ?

Best Answer

I have found the answer :

To access the temporal properties of a layer, use the temporalProperties() method of the QgsVectorLayer class. From here, use the setIsActive() method to active temporal properties, setStartField() to choose the field where your dates are (takes a string input), setAccumulateFeatures(Bool) if you like, and setMode() to choose between the available modes : same field for start and end, diferrents fields etc... this method takes a VectorTemporalMode() available here. To use it, just pass an int between 0 and 5 to choose the mode from the list given there. Note that you have to type qgis.core.Qgis.VectorTemporalMode(int) to use it.

Bonus : How to connect the temporal controller widget to a map canvas if you want to create a plugin or a script that opens a new QT window :

canvas = QgsMapCanvas() 
controler = QgsTemporalControllerWidget(the qtobject where you will put it) 
controler_to_be_used_by_canvas =  controler.temporalController()
 
canvas.setTemporalController(controler_to_be_used_by_canvas)

And here you can make a script that opens a new window in QGIS using PyQT5 from QtDesigner, set temporal layers and have a user friendly interface that allows to click and see a route being drawn on the canvas

TL;DR

To get all features of a layer by the layer name you do not need to activate it. Just use

name = 'counties'
layer = QgsProject.instance().mapLayersByName( name )[0]
poles = layer.getFeatures()
for pole in poles:
    if is_north(pole):
        print('it is the north pole')

Active Layer

First of all, you do not need to care about the active layer. The active layer is the layer which is currently selected in the layer tree and therefore is nice for two things

letting the user select a layer to operate on
selecting a layer for quickly testing code from the python console

The second one is handy when you are developing, the first one is what all the maptools are based on: the currently selected layer (the active one) is modified, selected, deleted...

Methods to access layers

However, you seem to want to access layers not based on user input but based on something else.

Identifying layers

All layers have

An id that needs to be unique
A name that is not necessarily (but often) unique and can be changed by the user
A reference (also often referred to as pointer but in python the two terms are interchangeable) that is unique and stable for the lifetime of a layer during the application run time and can be assigned to a variable (e.g. vlayer is a reference to the currently active layer in your example).
Properties like the URI (table name etc.)

If you already have a reference to the layer (because you created/added it in your plugin) just use that one.

If you don't, think about what property you want to use to get access to the layer. Most likely something that is stable (the layer id is very stable for the lifetime of a project but always is different for different projects), the name is user adjustable, the table may depend on the data source.

Accessing layers

There is the map layer registry which lets you access layers. It manages references to all layers. This used to be called QgsMapLayerRegistry, but that is no longer available in QGIS 3, so QgsProject can be used instead.

registry = QgsProject.instance()

If you have the layer id go with

layer = registry.mapLayer( id )

If you have the layer name

layer = registry.mapLayersByName( name )[0] # The method returns a list since it can be ambiguous, 0 picks the first entry in the list

If you have something else you have to write your own code:

for lyr in registry.mapLayers().values():
    if lyr.dataProvider().dataSourceUri().table() == 'mytable':
        layer = lyr
        break

Or a shorthand that does the same and makes you feel more hacker'ish but will make the people who will have to maintain the code later on cost some extra time to decipher:

layer = (l for l in registry.mapLayers().values() if l.dataProvider().dataSourceUri().table() == 'mytable').next()

Best Answer

Related Solutions

[GIS] Setting vector layer custom properties using PyQGIS

PyQGIS Layers – Activating Layer by Name in QGIS 2

TL;DR

Active Layer

Methods to access layers

Identifying layers

Accessing layers

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