import Blender

# Get current scene
scn = Blender.Scene.GetCurrent()

# Get all objects
objects = Blender.Object.Get()

# Get object with specified name
someobject = Blender.Object.Get('Plane')

# Select all objects
for ob in objects:
	ob.select(1)
	Blender.Redraw()
	

# Unselect all objects
for ob in objects:
	ob.select(1)
	Blender.Redraw()
	
# Make the first object active
scn.objects.active = objects[0]

# No active object
scn.objects.active = None