# Caching Long-Running Function Results

written by Eric J. Ma on 2019-10-18

I found this nifty tool for caching the results of long-running functions: cachier. This is useful when we’re building, say, Python applications for which quick interactions are necessary, or for caching the results of a long database query.

How do we use it? Basically it’s nothing more than a decorator!

Let’s imagine I have a long-running function as below.

def long_running_function(arg1, arg2):
# stuff happens
return result


Turns out, if you have a need to cache the result in a lightweight fashion, you can simply add cachier:

from cachier import cachier

@cachier()
def long_running_function(arg1, arg2):
# stuff happens
return result


The result is stored in your home directory, so the cache is accessible to you.

One nice thing cachier also offers is the ability to set a time duration after which the cache goes stale. This can be useful in situations where you know that you need to refresh the cache, such as a database query that may go stale because of new data added into it. This is done by specifying the stale_after keyword argument:

from cachier import cachier
from datetime import timedelta

# Re-cache result after 1 week.
@cachier(stale_after=timedelta(weeks=1))
def long_running_function(arg1, arg2):
# stuff happens
return result


If you need to reset the cache manually, you can always do:

long_running_function.clear_cache()


There are other advanced features that cachier provides, and so I’d encourage you to go and take a look at it!