Can you add a light source in blender using python

Answer is Yes!

Look at the recent Python API.

The example below creates a new Lamp object and puts it at the default location (5, 5, 5) in the current scene:

(Blender 2.63)

The script should look like this:

import bpy

scene = bpy.context.scene

# Create new lamp datablock
lamp_data = bpy.data.lamps.new(name="New Lamp", type='POINT')

# Create new object with our lamp datablock
lamp_object = bpy.data.objects.new(name="New Lamp", object_data=lamp_data)

# Link lamp object to the scene so it'll appear in this scene
scene.objects.link(lamp_object)

# Place lamp to a specified location
lamp_object.location = (5.0, 5.0, 5.0)

# And finally select it make active
lamp_object.select = True
scene.objects.active = lamp_object

Blender 2.80 broke the old API, most steps changed. Updated code below.

import bpy

# create light datablock, set attributes
light_data = bpy.data.lights.new(name="light_2.80", type='POINT')
light_data.energy = 30

# create new object with our light datablock
light_object = bpy.data.objects.new(name="light_2.80", object_data=light_data)

# link light object
bpy.context.collection.objects.link(light_object)

# make it active 
bpy.context.view_layer.objects.active = light_object

#change location
light_object.location = (5, 5, 5)

# update scene, if needed
dg = bpy.context.evaluated_depsgraph_get() 
dg.update()