4.5. Saving and Loading

Saving

Let us create a simple transition that counts how many times the user visits:

def visits() -> DialogueFlow:
    transitions = {
        'state': 'start',
        '`It\'s your` #VISITS `visit!`': 'end'
    }

    macros = {
        'VISITS': MacroVisits()
    }

    df = DialogueFlow('start', end_state='end')
    df.load_transitions(transitions)
    df.add_macros(macros)
    return df

• #4: calls the macro #VISITS defined in #7.

MacroVisits can be defined as follow:

class MacroVisits(Macro):
    def run(self, ngrams: Ngrams, vars: Dict[str, Any], args: List[Any]):
        vn = 'VISITS'
        if vn not in vars:
            vars[vn] = 1
            return 'first'
        else:
            count = vars[vn] + 1
            vars[vn] = count
            match count:
                case 2: return 'second'
                case 3: return 'third'
                case default: return '{}th'.format(count)

• #10-13: uses the match statements to return the appropriate literal.

Output

S: It's your first visit!

The challenge is that we must save the number of visits to make this macro effective (and correct). This can be achieved by saving the variable dictionary into a binary file using the built-in Python object serialization called pickle:

def save(df: DialogueFlow, varfile: str):
    df.run()
    d = {k: v for k, v in df.vars().items() if not k.startswith('_')}
    pickle.dump(d, open(varfile, 'wb'))

save(visits(), 'resources/visits.pkl')

• #1: takes a dialogue flow df and a file path varfile for saving the variable dictionary to.

• #3: creates a dictionary by copying only user-generated variables.

• #4: opens a writable (w) and binary (b) file and dumps the dictionry object into the file.

After running this code, you will see the visits.pkl file saved under the resources directory.

Loading

The following code shows how to load the saved dictionary to a new dialogue flow:

def load(df: DialogueFlow, varfile: str):
    d = pickle.load(open(varfile, 'rb'))
    df.vars().update(d)
    df.run()
    save(df, varfile)

• #1: takes a dialogue flow df and a file path varfile for loading the variable dictionary from.

• #2: opens a readable (r) and binary (b) file and loads the object as a dictionary.

• #3: adds all variables in the loaded dictioinary to the variable dictionary of df.

• #5: saves the new variable dictionary to the same file.

2nd Visit

S: It's your second visit!

3rd Visit

S: It's your third visit!

4th Visit

S: It's your 4th visit!