2. LRU Cache

In this tutorial use of lru_cache function is demonstrated.

This function is used a lot like functools.lru_cache function and helps by saving results of heavy function execution and avoiding recalculation.

Caches are kept in a library-wide singleton and are cleared at the end of each turn.

Maximum size parameter limits the amount of function execution results cached.

# installing dependencies
%pip install -q dff

Note: you may need to restart the kernel to use updated packages.

from dff.script.conditions import true
from dff.script import Context, TRANSITIONS, RESPONSE, Message
from dff.script.labels import repeat
from dff.pipeline import Pipeline
from dff.utils.turn_caching import lru_cache
from dff.utils.testing.common import (
    check_happy_path,
    is_interactive_mode,
    run_interactive_mode,
)

external_data = {"counter": 0}

@lru_cache(maxsize=2)
def cached_response(_):
    """
    This function will work exactly the same as the one from previous
    tutorial with only one exception.
    Only 2 results will be stored;
    when the function will be executed with third arguments set,
    the least recent result will be deleted.
    """
    external_data["counter"] += 1
    return external_data["counter"]


def response(ctx: Context, _, *__, **___) -> Message:
    if ctx.validation:
        return Message()
    return Message(
        text=f"{cached_response(1)}-{cached_response(2)}-{cached_response(3)}-"
        f"{cached_response(2)}-{cached_response(1)}"
    )

toy_script = {
    "flow": {"node1": {TRANSITIONS: {repeat(): true()}, RESPONSE: response}}
}

happy_path = (
    (Message(), Message("1-2-3-2-4")),
    (Message(), Message("5-6-7-6-8")),
    (Message(), Message("9-10-11-10-12")),
)

pipeline = Pipeline.from_script(toy_script, start_label=("flow", "node1"))

if __name__ == "__main__":
    check_happy_path(pipeline, happy_path)
    if is_interactive_mode():
        run_interactive_mode(pipeline)

(user) >>>
 (bot) <<< text='1-2-3-2-4'
(user) >>>
 (bot) <<< text='5-6-7-6-8'
(user) >>>
 (bot) <<< text='9-10-11-10-12'