Getting list of layer names using PyQGIS?

I need a list containing the names of all the layers in a QGIS session. I did the task as

layersNames = []
for i in self.iface.mapCanvas().layers():
   layersNames.append(str(i.name()))

but this has the problem that only the names for the visible layers are extracted. How can I get a list with the names of all (visible or not) layers using PyQGIS?

Answer

QgsMapLayerRegistry.instance().mapLayers() will give you all layers that are opened.

If you want the names then:

names = [layer.name() for layer in QgsMapLayerRegistry.instance().mapLayers().values()]

names will be a list of layer names

or using a normal function:

for layer in QgsMapLayerRegistry.instance().mapLayers().values():
    print layer.name()