can't erase dbf and shp pyQGIS

Question

I created a script in which I run numerous algorithms from processing. Each resulting layer is stored in a shp file. I just want to keep the final layer and delete the others, but when I want to erase them while QGIS is still open, they are still in usewhile not shown in the layers list, I can't erase them. This is a problem when I run my script a 2nd time because it doesn't work.

I tried removing the layers with QgsMapLayerRegistry.instance().addMapLayer(layer) QgsMapLayerRegistry.instance().removeMapLayer(layer.id()) but I had no success so far... .prj .qpj and .shx are deleted, only remains .dbf and .shp.

Here is the code

import processing
from qgis.core import *

layer=processing.getObject("carte")
layer.invertSelection()

processing.runalg('qgis:fixeddistancebuffer', layer, "20","5",False, "c:/Users/LENOVO/Desktop/zones/tampon+.shp")
processing.runalg('qgis:dissolve', "c:/Users/LENOVO/Desktop/zones/tampon+.shp", True, None, "c:/Users/LENOVO/Desktop/zones/dissolve.shp")

tampon=QgsVectorLayer("c:/Users/LENOVO/Desktop/zones/tampon+.shp", 'finale','ogr')
QgsMapLayerRegistry.instance().addMapLayer(tampon)
QgsMapLayerRegistry.instance().removeMapLayer(tampon.id())

processing.runalg('qgis:fixeddistancebuffer', "c:/Users/LENOVO/Desktop/zones/dissolve.shp", "-20","5",False, "c:/Users/LENOVO/Desktop/zones/carte_finale.shp")
dissolve=QgsVectorLayer("c:/Users/LENOVO/Desktop/zones/dissolve.shp", 'finale','ogr')

QgsMapLayerRegistry.instance().addMapLayer(dissolve)
QgsMapLayerRegistry.instance().removeMapLayer(dissolve.id())
layer = QgsVectorLayer("c:/Users/LENOVO/Desktop/zones/carte_finale.shp", 'finale','ogr')
QgsMapLayerRegistry.instance().addMapLayer(layer)

Answer 1

Instead of writing an output for each algorithm (and then having to load and remove them), you can instead save them as temporary layers using the None parameter and call these as inputs for any subsequent algorithms. Not tested but the following should hopefully work:

import processing
from qgis.core import *

layer=processing.getObject("carte")
layer.invertSelection()

tampon_plus = processing.runalg('qgis:fixeddistancebuffer', layer, "20","5",False, None)
dissolve = processing.runalg('qgis:dissolve', tampon_plus['OUTPUT'], True, None, None)
carte_finale = processing.runalg('qgis:fixeddistancebuffer', dissolve['OUTPUT'], "-20","5",False, "c:/Users/LENOVO/Desktop/zones/carte_finale.shp")

layer = QgsVectorLayer("c:/Users/LENOVO/Desktop/zones/carte_finale.shp", 'finale','ogr')
QgsMapLayerRegistry.instance().addMapLayer(layer)