Stateful bots

Building Chatbots in Python

Alan Nichol

Co-founder and CTO, Rasa

What do we mean by stateful?

"I love stateless systems!"

"don't what have drawbacks?"

"don't they have drawbacks?"

State machines

Browsing
Providing address, billing info
Order complete

Implementing a state machine

INIT = 0
CHOOSE_COFFEE = 1
ORDERED = 2

Example rules:

policy_rules = {
    (INIT, "order"): (CHOOSE_COFFEE, "ok, Columbian or Kenyan?"),
    (CHOOSE_COFFEE, "specify_coffee"): 
    (ORDERED, "perfect, the beans are on their way!"),
}

Using the state machine

state = INIT
def respond(state, message):
   (new_state, response) = policy_rules[(state,
                                   interpret(message))]
   return new_state, response

def send_message(state, message):
    new_state, response = respond(state, message)
    return new_state

state = send_message(state, message)

Let's practice!

Building Chatbots in Python