##Example=name
##Folder=folder

# Import required modules
import glob, os
from qgis.core import QgsVectorLayer, edit

# Iterate through all files only ending in .shp (i.e. shapefiles)
for shapefile in glob.glob(Folder + "/*.shp"):
    # Get file name
    name = os.path.splitext(os.path.basename(shapefile))[0]
    # Read file as a vector layer
    layer = QgsVectorLayer(shapefile, name, 'ogr')
    # Set the origin field
    origin_field = 'oldField'
    # Set the target field
    target_field = 'newField'
    # Get index of target field
    idx = layer.fieldNameIndex(target_field)
    # Start editing the layer
    with edit(layer):
        # Iterate through each feature
        for feat in layer.getFeatures():
            # Copy values from origin field to target field
            layer.changeAttributeValue(feat.id(), idx, feat[origin_field])