Build a simple ChatBot in Python with RASA — Part 2

We are building an amazing chatbot Lemonade

In this section we are going to work on the Dialogue part for “building a simple chatbot using RASA conversational AI solution”.

If you haven’t went through part 1 I recommend you to first read part 1 and only then read this one.

Now things are getting interesting, chatbot wise — till now we’ve built the NLP/U part and now we are going to work on the dialogue side.

As I mentioned in part 1, for every chatbot that actually do a little bit more that just question answering, the very basic one is a chatbot that supports “slot filling”, which means (in our example) to interact with the user to get the mandatory slots that it needs (according to the “domain definition” — don’t worry we’ll get to that later on).

One slot filling scenario could be:

• user: “I want Pizza” ; #missing slots: [size, toppings, etc.]
• bot: “what size?”
• user: “large”
• bot: “Which toppings would you like?”
• user: “Olives”

In this example we have 2 interactions with the user — 2 slots to fill.

Building the Dialogue

Similar to what we’ve built in the NLU (part 1 mentioned above) we should create the domain and the training data.

Building the Domain

Here we would create the file chat_domail.yml.

You can use this file:

Pay attention to the last one — more info below on the explanation part.

But if you create your own or changing this one, it is always a good practice to validate the format (this is a fragile format and things won’t work in case you break it):

Link to online yml validation.

Let’s try to explain the file above.

• Intents — is the parent structure, usually are the supported actions of your bot (but there are exceptions)
• Entities — are the words that you want the bot to extract from the free text
• Slots — Defining them here, is like saying to the bot which entities to track through the dialogue, for example, if the user is saying: “I want pizza”, we want the bot to interact with the user to get the “size” or the “topping” slots fulfilled.
• Actions — are either utterances, which means, the output that we want to send the user, or you can actually create your own class that inherent form Action. In our example its: “actions.ActionOrderPizza”, here again Rasa has a very cool interface, you should inherent from Class Action and add your logic in the derived class according to what you need, here is an example — create the file action.py:

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In the above example I created it as “stubs” no real logic there, just for the sake of the example.

Building the Training Data for the Dialogue

Here we are going to build a mark down file, we’ll named it: stories.md, as the name implies here we describe the possible dialogue flows as user stories.

Here you may raise a concern that its a very manual process but don’t worry RASA has a great tool for you to online train you dialogue! or even more load pre-trained dialogues.

But first let’s create a very short and basic flow, and train the dialogue model, we’ll get back to the online training later on.

For the basic flow you can use this file stories.md:

Pay attention that in the above flow we are covering the following scenario:

1. Bot: “Hello, how can I help you?”
2. User: “I want pizza” #missing the slots: “size” and “toppings”
3. Bot: “What size?”
4. User: “large”
5. Bot: “what toppings would like on your pizza?”
6. User: “cheese”

Now we are ready to train a dialogue using the above training data.

Let’s write some code, you can use this file:

Now run:

python dialogue_model.py

Note: the code above is running with no errors on Python3 but for some reason I had some issues with Python2.

If everything went well you should have the model trained and the output is under, models/dialogue/, it should look like this:

NOW we are ready for the online training! yay!!!

As I promised RASA has an amazing capability to online train your bot and create a much more elaborated stories.md file for you to use after online training session is finished.

Now create the online_train.py:

No we are ready to run:

python online_train.py

You should get an interactive session in which you should follow the expected flow, for example:

1. In the first green line it says that the bot has been loaded and is waiting for the user input.
2. Next we type: “hi”
3. Now you can see that the system prints the “Chat history”:

• we can see that the flow is correct:
• bot did: action_listen
• user said: hi
• whose intent is: greet

4. Now the system is waiting for your feedback, in this case the flow is correct, so we should type: 2.

5. You can continue doing this as long as you want, when you finish type “0” to export the new stories.md file (give it new name, such: “stories_v1.md”).

Now replace the previous stories file (back it up first!) or concatenate them in the same stories file, that way you should have more and more training data!

That’s it — now the last part is to test it — more to come…

Please feel free ask question here or go to relevant gitter section:

RasaHQ/rasa_core_machine learning based dialogue engine for conversational software_gitter.im