You can do this by adding an event handler to the frame change event.

 import bpy
 
 def my_handler(scene):
 
 fm = bpy.data.scenes['Scene'].frame_current
 
 if fm >= 1:
 lampStrength = 100
 if fm >= 50:
 lampStrength = 200
 if fm >= 100:
 lampStrength = 300
 if fm >= 150:
 lampStrength = 400 
 
 scene.objects['Point'].data.node_tree.nodes['Emission'].inputs['Strength'].default_value=lampStrength
 
 print("lamp strength: " + str(lampStrength))
 
 
 def register():
 bpy.app.handlers.frame_change_post.append(my_handler)
 
 def unregister():
 bpy.app.handlers.frame_change_post.remove(my_handler)
 
 if __name__ == "__main__":
 register() 


*Credit for frame change portion of script here:* https://blender.stackexchange.com/questions/27465/running-a-script-for-each-frame