gistfile1.py

class Selection(object):
    def __init__(self, layer=None):
        self._layer = layer
        
    @property
    def layer(self):
        return self._layer or iface.activeLayer()
        
    def update(self, **kwargs):
        debug = kwargs.get('debug', False)
        if debug:
            del kwargs['debug']
        self.layer.startEditing()
        for feature in self:
            for field, value in kwargs.iteritems():
                feature[field] = value
            if debug:
                print "Updated {} with {}".format(feature.id(), str(kwargs))
            self.layer.updateFeature(feature)
    
    def __getitem__(self, attr):
        return Selection(QgsMapLayerRegistry.instance().mapLayersByName(attr)[0])
    
    def __iter__(self):
        return iter(self.layer.selectedFeatures())
        
    def __len__(self):
        return self.layer.selectedFeatureCount()

selection = Selection()

Usage.md

Usage:

>>> selection.update(field1=1, field2="balh")

>>> selection['mylayer'].update(field1=1, field2="balh")