Adding fields to temporary layer using PyQGIS?

Question

I want to add some fields in a temporary layer in order to use it in another process.

What I tried to do is below :

    shp_result = processing.run(
        'native:pixelstopoints',
        {
            'INPUT_RASTER': raster_redim['OUTPUT'],
            'RASTER_BAND': 1,
            'FIELD_NAME': 'VALUE',
            'OUTPUT': 'TEMPORARY_OUTPUT'
        },
        is_child_algorithm=True,
        context=context,
        feedback=feedback)

    # On ajoute 2 autres champs pour contenir les coordonnées X, Y
    # du point de cours d'eau associé au point d'intérêt
    self.maCouche = QgsVectorLayer(shp_result['OUTPUT'], self.nom[0], 'ogr')

    prov = self.maCouche.dataProvider()
    prov.addAttributes([QgsField("X", QVariant.Double)])
    prov.addAttributes([QgsField("Y", QVariant.Double)])
    self.maCouche.updateFields()

    dist_fNul = processing.run(
        'grass7:v.distance',
        {
            'from': self.maCouche.source(),
            'from_type':[0,1,3],
            'to': parameters[self.MASK],
            'to_type':[0,1,3],
            'dmax':-1,
            'dmin':-1,
            'upload':[1,2,3],
            'column':['VALUE', 'X', 'Y'],
            'to_column':None,
            'from_output': parameters[self.OUTPUT],
            'output':'TEMPORARY_OUTPUT',
            'GRASS_REGION_PARAMETER':None,
            'GRASS_SNAP_TOLERANCE_PARAMETER':-1,
            'GRASS_MIN_AREA_PARAMETER':0.0001,
            'GRASS_OUTPUT_TYPE_PARAMETER':0,
            'GRASS_VECTOR_DSCO':'',
            'GRASS_VECTOR_LCO':'',
            'GRASS_VECTOR_EXPORT_NOCAT':False
        },
        is_child_algorithm=True,
        context=context,
        feedback=feedback
        )

But the final result is not what I expect : only the 'VALUE' field is created instead of giving me tree fields 'VALUE', 'X', 'Y' (in dist_fNul).

Answer 1

I want to add some fields in a temporary layer in order to use it in another process.

What I tried to do is below :

 shp_result = processing.run(
    'native:pixelstopoints',
    {
        'INPUT_RASTER': raster_redim['OUTPUT'],
        'RASTER_BAND': 1,
        'FIELD_NAME': 'VALUE',
        'OUTPUT': 'TEMPORARY_OUTPUT'
    },
    is_child_algorithm=True,
    context=context,
    feedback=feedback)

# On ajoute 2 autres champs pour contenir les coordonnées X, Y
# du point de cours d'eau associé au point d'intérêt
self.maCouche = QgsVectorLayer(shp_result['OUTPUT'], self.nom[0], 'ogr')

prov = self.maCouche.dataProvider()
prov.addAttributes([QgsField("X", QVariant.Double)])
prov.addAttributes([QgsField("Y", QVariant.Double)])
self.maCouche.updateFields()

dist_fNul = processing.run(
    'grass7:v.distance',
    {
        'from': self.maCouche.source(),
        'from_type':[0,1,3],
        'to': parameters[self.MASK],
        'to_type':[0,1,3],
        'dmax':-1,
        'dmin':-1,
        'upload':[1,2,3],
        'column':['VALUE', 'X', 'Y'],
        'to_column':None,
        'from_output': parameters[self.OUTPUT],
        'output':'TEMPORARY_OUTPUT',
        'GRASS_REGION_PARAMETER':None,
        'GRASS_SNAP_TOLERANCE_PARAMETER':-1,
        'GRASS_MIN_AREA_PARAMETER':0.0001,
        'GRASS_OUTPUT_TYPE_PARAMETER':0,
        'GRASS_VECTOR_DSCO':'',
        'GRASS_VECTOR_LCO':'',
        'GRASS_VECTOR_EXPORT_NOCAT':False
    },
    is_child_algorithm=True,
    context=context,
    feedback=feedback
    )

But the final result is not what I expect : only the 'VALUE' field is created instead of giving me tree fields 'VALUE', 'X', 'Y' (in dist_fNul).

* Alternative method *

Finally, I decided to save the resulting file of "shp_result" and use it clearly in the second process and, once this is finished, I delete the saved file.