caching

caching.py

# Utility function to help with local prototyping to minimize trips to fetch data.
# Import the function and decorate any data-retrieval function to use cache if
# available, make one if not. Remove the decorator before submitting to production.
import cPickle as pickle
import logging
import os
from functools import wraps


THIS_DIR = os.getcwd()


def persist_cache_to_disk(filename):
    def decorator(original_func):

        @wraps(original_func)
        def new_func(*args, **kwargs):
            # Use the cache if available
            if os.path.exists(filename):
                logging.info("Cache found at {}, loading it now".format(
                    os.path.join(THIS_DIR, filename)
                ))
                with open(filename, 'r') as f:
                    cache = pickle.load(f)

                logging.info('Cache loaded')

            else:
                cache = None

            if cache is None:
                logging.info("No cache found at {}, getting data".format(
                    os.path.join(THIS_DIR, filename)
                ))
                cache = original_func(*args, **kwargs)

                logging.info("Persisting data to cache at {}".format(
                    os.path.join(THIS_DIR, filename)
                ))
                pickle.dump(cache, open(filename, "w"))
                logging.info("Finished persisting data")

            return cache

        return new_func

    return decorator