How to store the result of an executed function and re-use later?

Question

E.g., I have:

def readDb():
    # Fetch a lot of data from db, spends a lot time
    ...
    return aList

def calculation():
    x = readdb()
    # Process          


        

Answer 1

Updated answer for modern Python

For anyone still searching for how to do this, the standard library functools includes a decorator function @functools.lru_cache to do this.

For example (from the docs):

@lru_cache(maxsize=32)
def get_pep(num):
    'Retrieve text of a Python Enhancement Proposal'
    resource = 'http://www.python.org/dev/peps/pep-%04d/' % num
    try:
        with urllib.request.urlopen(resource) as s:
            return s.read()
    except urllib.error.HTTPError:
        return 'Not Found'

This would store the last 32 calls to get_pep and when it is called with the same argument, the cached value will be returned.