__author__ = 'thoth'

import bpy

def mission1(obj):
    lamp = obj.data

    e_node = lamp.node_tree.nodes["Emission"]

    data_path = 'nodes["Emission"].inputs[1].default_value'
    for fr in [100, 130, 150, 200, 300]:
        fr2 = fr+10
        e_node.inputs[1].default_value = 20
        lamp.node_tree.keyframe_insert(data_path=data_path, frame=fr)
        e_node.inputs[1].default_value = 100
        lamp.node_tree.keyframe_insert(data_path=data_path, frame=fr2)

    for fc in lamp.node_tree.animation_data.action.fcurves:
        for kp in fc.keyframe_points:
            kp.interpolation = 'CONSTANT'


mission1(bpy.context.active_object)