Changing number of decimal places of a String variable within a Vector Layer using PyQGIS

Question

I have earthquake data and within the data, there are magnitude, longitude and latitude values. However, these values have around 6/7 decimal places but I would like to only have 2 decimal places for each value, when I export my map. I add the earthquake event through QgsVectorLayer rather than a CSV format when using python and I can access features such as magnitude, longitude and latitude, by using feat['magnitude']), as can be seen below:

I then add each feature to the layout exporter, ready to export. I have tried various ways to only get 2 decimal places on each feature but non have prevailed as of yet. The ways I have tried are: to_real(ID), format_number(ID, decimal place), float(ID), round($ID, decimal places) and layer.dataProvider().addAttributes([QgsField("fieldname", QVariant.String, "String", 10, 2)]). I may have done part of the code wrong though, hence why it did not work. Each feature is within a string variable but I can not seem to find a way how to convert to double or real. A small snippet of my map is included below where the values of magnitude, longitude and latitude can be seen, so that I would like each value to say 4.39 (Mag), -72.02 (Long) and 6.40 (Lat). Hope this makes sense.

Answer 1

Edit: definitive answer

mag.setText("Magnitude: " + str(round(float(feat['magnitude']), 2)))

Archived answer for people using Atlas

You can find below a sample to illustrate. This sample is using an existing QgsLayoutItemLabel you must select manually to work instead of one you created like your sample. I'm also in the context of an atlas to loop each feature.

layout_name = 'your_layout_name'
project = QgsProject.instance()
projectLayoutManager = project.layoutManager()
layout = projectLayoutManager.layoutByName(layout_name)


# You should select your label layout item before runnong this line of code
existing_layout_item_label = layout.selectedLayoutItems()[0]

text = "[% attribute(@atlas_feature ,'NAME')%]\nRounded lat : [%round(to_real(attribute(@atlas_feature ,'LATITUDE')),2)%]"
existing_layout_item_label.setText(text)

layout.refresh()