Set extent of Layout Item Map

Question

I work on a QGIS Plugin in python. This plugin import in QGIS project several print layout (A4/A3/Landscape/Portait format) from a directoty of my laptop to the layout manager. The plugin add also a vector layer in my QGIS project. I would like that when I open a layout from the layout manager, the map of this layout is centered on the extent of the layer in my project. I have tried the code below but it does not zoom in correctly on the layer.

project = QgsProject.instance()

zip_layer = QgsVectorLayer("C:/Users/Thysma/Documents/Stage/Data/zip.shp", "Aire d'étude",'ogr')                   
QgsProject.instance().addMapLayer(zip_layer)

composition = QgsPrintLayout(project)
document = QDomDocument()
template_file = open('C:/Users/Thysma/Documents/Stage/Composeurs/A3 Paysage.qpt')
template_content = template_file.read()
template_file.close()
document.setContent(template_content)
composition.loadFromTemplate(document, QgsReadWriteContext()) 
project.layoutManager().addLayout(composition)

layout = project.layoutManager().layoutByName('A3 Paysage')        
map = layout.itemById("map")      
map.setExtent(zip_layer.extent())      
map.attemptMove(QgsLayoutPoint(0.150, 21.610, QgsUnitTypes.LayoutMillimeters))
map.attemptResize(QgsLayoutSize(342.235, 275.240,QgsUnitTypes.LayoutMillimeters))

The zoom made gives me the following rendering (the map is not zoomed in on the total extent of the layer):

Answer 1

Instead of setExtent() you should use zoomToExtent() method.

E.g.

...
layer_extent = zip_layer.extent()
map.zoomToExtent(layer_extent)

If you wish too zoom out very slightly from the layer extent you can use the grow() method on the QgsRectangle layer_extent object.

E.g.

...
layer_extent = zip_layer.extent()
layer_extent.grow(0.1)#pass a sensible value depending on crs used and map scale
map.zoomToExtent(layer_extent)

The value you pass to the grow() method will depend on size/scale of your layer and whether you are working with meter or geographic degree units etc.