How to improve a simple caching mechanism in Python?

Question

just registered so I could ask this question.

Right now I have this code that prevents a class from updating more than once every five minutes:

now = datetime.now()
delta = now - myClass.last_updated_date
seconds = delta.seconds

if seconds > 300
    update(myClass)     
else
    retrieveFromCache(myClass)

I'd like to modify it by allowing myClass to update twice per 5 minutes, instead of just once.

I was thinking of creating a list to store the last two times myClass was updated, and comparing against those in the if statement, but I fear my code will get convoluted and harder to read if I go that route.

Is there a simpler way to do this?

it is, I generalized the small piece I'm working on right now — user1420913
– user1420913, Commented Jan 30, 2013 at 23:56
Count how many times you've updated since seconds and incorporate that in your logic. — Morten Jensen
– Morten Jensen, Commented Jan 30, 2013 at 23:57

Nix · Accepted Answer · 2013-01-31 00:02:29Z

1

You could do it with a simple counter. Concept is get_update_count tracks how often the class is updated.

if seconds > 300 or get_update_count(myClass) < 2:
    #and update updatecount
    update(myClass)     
else:
    #reset update count
    retrieveFromCache(myClass)

Im not sure how you uniquely identify myClass.

update_map = {}

def update(instance):
     #do the update
     update_map[instance] = update_map.get(instance,0)+1

def get_update_count(instance):
     return update_map[instance] or 0

edited Jan 31, 2013 at 0:02

answered Jan 30, 2013 at 23:57

Nix

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1 Comment

user1420913 Over a year ago

Ah yep that is so much cleaner. Thanks so much.

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