Share data between functions called by external library

Question

I'm writing a slackbot using bolt_python which consists of writing functions that are called during events. Multiple of the events I want to respond to use the same data that I get from an external API. I'd like to avoid calling the API multiple times for the exact same data, so I'd like to cache it and share the cache.

I could make the cache use a global variable, but no one likes that.

Here's what the version using a global might look like.

dumb_global = {}

@app.command('\foo') 
def foo_command(command, logger, say):
    if len(dumb_global) < 1:
        dumb_global = do_lots_of_io_and_networky_stuff()
    say(something_useful(dumb_global))

@app.action('button-click')
def button_click(action, logger, say):
    if len(dumb_global) < 1:
        dumb_global = do_lots_of_io_and_networky_stuff()
    say(something_else_useful(dumb_global))

What's the best way to do this?

Thanks!

Answer 1 · 2025-11-20 01:18:54Z

Well, you can use a class to handle state, its better than a raw global and you are wrapping your cache in a class which is explicit that is sharing state. So the data gets loaded on the first call and then it reused after that.

class BotCache:
    def __init__(self):
        self.data = None
    
    def get_data(self):
        if self.data is None:
            self.data = do_lots_of_io_and_networky_stuff()
        return self.data

cache = BotCache()

@app.command('\foo') 
def foo_command(command, logger, say):
    say(something_useful(cache.get_data()))

@app.action('button-click')
def button_click(action, logger, say):
    say(something_else_useful(cache.get_data()))

here you can add cache invalidation logic later without touching the events handlers. Also as a recomendation additional you can use functools.lru_cache for automatic expriation and the decorator handle that cache automatic. heres the code recomended

from functools import lru_cache
import time

@lru_cache(maxsize=1)
def get_data(cache_key):
    return do_lots_of_io_and_networky_stuff()

data = get_data(int(time.time()) // 300)  # here it does the refres at 5min

(FYI just change the cache key when you want to fresh data.)

I noticed into bold-python there is an issue tracker active, if you need addittional help, you can check directly with them if my answer didnt work.

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Share data between functions called by external library

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Share data between functions called by external library

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