PyQGIS -- write print composer to project file

Question

Is there a way to write a print composer to a QGS project file via PyQGIS, so that when the project file is opened later, that print composer is available?

I am able to successfully do the following:

• load and manipulate a project (load layers, etc)
• load a print composer template (QPT file) and manipulate the composer elements
• save the modified QGS file
• export the print composer map to PDF

However, I can't figure out how to save that print composer to the QGS file.

Essentially that means that if I want to go into the QGS file afterwards and make edits to the map generated from the print composer, I need to load a new print composer from template and redo all the edits from scratch (map title, extents, map notes, etc).

The following code works to load a composer from a QPT template file and export the map as PDF, but does not save the composer with the QGS file:

#initialize QGIS
app = QgsApplication([], True)
app.initQgis()

#set project and template paths
project_path = "/mypath/myproject.qgs"
template_path = "/mypath/mytemplate.qpt"

#get canvas and load project
canvas = QgsMapCanvas()
project = QgsProject.instance()
project.read(QFileInfo(project_path))

#load print composer template
template_file = file(template_path)
template_content = template_file.read()
template_file.close()

document = QDomDocument()
document.setContent(template_content)
composition = QgsComposition(canvas.mapSettings())
composition.loadFromTemplate(document)

#refresh after manipulating composer elements
composition.refreshItems()

#export to PDF and also save a QGS file
composition.exportAsPDF('myfile.pdf')
project.write(QFileInfo('myfile.qgs'))

I believe I must be missing something either in, or prior to, the last line of code:

project.write(QFileInfo('myfile.qgs'))

to add the composer to the QGS file.

Answer 1

QgsLayoutManager handles compositions stored directly in a project rather than as template files

layoutManager=project.layoutManager()

#add a composition
layoutManager.addComposition(composition)

#print composition names
comps=layoutManager.compositions()
for comp in comps:
    print ('Layout: {}'.format(comp.name()))

#load a composition by name
composition=layoutManager.compositionByName('My Composition')