How to call a temporary layer from another python script in QGIS?

Question

I wrote several python scripts called by my main.py script. In one of those scripts I create a vector layer by polygonizing a raster layer. As the layer is really heavy and as I don't need it as an output, I create it in memory.

result = processing.runalg('gdalogr:polygonize',layer,"lu_majorit", None)
polygonLayer = processing.getObject(result['OUTPUT'])

Then I can use the layer in my file. But I would like to use this layer from another script and I don't succeed.

Here is what I've tried :

in my first script :

result = processing.runalg('gdalogr:polygonize',layer,"lu_majorit", None)
polygonLayer = processing.getObject(result['OUTPUT'])
return polygonLayer

in my main:

polygonLayer=script1(...)
script2(polygonLayer,...)

in my second script :

cLayer =QgsVectorLayer("Polygon?crs=epsg:4326", "OUTPUT", "memory")

or:

cLayer =QgsVectorLayer("polygonLayer", "OUTPUT", "ogr")

Those two ways failed to load the layer.

I tried also by giving the path with : script 1 :

myfilepath= polygonLayer.dataProvider().dataSourceUri()
return myfilepath

script2:

cLayer =QgsVectorLayer(myfilepath, "OUTPUT", "ogr")

This way gives me an invalid syntax.

Does someone know how to do ?

• Hicham Zouarhi: instead of runalg you can use runandload ( load it to QgsMapLayerRegistry and use it later ) like here gis.stackexchange.com/questions/76594/…
• J.Delannoy: @HichamZouarhi When I replace runalg by runanload I get this message error : "polygonize has no attribute 'getitem'"

Answer 1

If both your python files are in the same directory, something like this should work:

script2

def myFunction():
 result = processing.runalg('gdalogr:polygonize',layer,"lu_majorit", None)
 polygonLayer = processing.getObject(result['OUTPUT'])
 return polygonLayer

main script

import script2 # for python file named script2.py
polygonLayer = script2.myFunction()

If they are not in the same directory you may use the sys.path.append() method to append the path of the python script you want to add:

sys.path.append('//path/to/other/script/directory')
import script2

• J.Delannoy: Thank you for your answer. My files are in the same directory and I tried this method. But this does not work. It failed to load the layer
• artwork21: Can you expand more on what you mean by "failed to load the layer"?
• J.Delannoy: It works !!! I think that I tried too many ways so I mixed up some ... So now that I cleaned my code to explain better my problem, there is no problem anymore. So thank you :)