cachepy 0.1

Caching results of functions in Python

Caching results of functions in Python.

Features

• Storing cached data either on disk or in memory

• Setting up time-to-live and the number of function calls for your cache

• Encryption of cached data (symmetric encryption (RSA) algorithm is used)

Note

• Encryption functionality requires pycrypto package to be installed

• When using cache-to-file functionality you have to to clean up (if needed) created file(s) manually

Examples

from cachepy import *

mycache = Cache() # cache to memory without encryption

@mycache
def my_heavy_function(x):
    """Performs heavy computations"""
    print('Hi, I am called...')
    return x**2

my_heavy_function(2)
# "Hi, I am called..." will be printed to stdout only once
my_heavy_function(2)

To store data to file, you need to create decorator as follows:

# create cache-to-file decorator
filecache = Cache('mycache.dat')

Its behaviour is the same as a memory-based one.

One can set up time-to-live and/or maximum number of retrievals for cached data when a decorator is created:

import time
from cachepy import *
# or from cachepy import Cache

cache_with_ttl = Cache(ttl=2) # ttl given in seconds

@cache_with_ttl
def my_heavy_function(x):
    """Performs heavy computations"""
    print('Hi, I am called...')
    return x**2

my_heavy_function(3)
my_heavy_function(3) # This will not print 'Hi, I am called ...'
time.sleep(2)
my_heavy_function(3) # 'Hi, I am called ...' will be printed again

cache_with_noc = Cache(noc=2) # Number-of-calls = 2

@cache_with_noc
def my_heavy_function(x):
    """Performs heavy computations"""
    print('Hi, I am called...')
    return x**2

my_heavy_function(3)
my_heavy_function(3) # This will not print 'Hi, I am called ...'
my_heavy_function(3) # 'Hi, I am called ...' will be printed again

It is easy to use both noc and ttl arguments on a cache decorator:

cache_with_noc_ttl = Cache(noc=2, ttl=1)

@cache_with_noc_ttl
def my_heavy_function(x):
    """Performs heavy computations"""
    print('Hi, I am called...')
    return x**2

my_heavy_function(3)
my_heavy_function(3) # This will not print 'Hi, I am called ...'
my_heavy_function(3) # This will print 'Hi, I am called ...'
time.sleep(2) # get ttl to be expired
my_heavy_function(3) # This will print 'Hi, I am called ...'

One can encrypt cached data by providing non-empty key argument as a password (RSA algo is used):

cache_to_file_ttl_noc = Cache('mycache.dat',
                               noc=2, ttl = 2, key='mypassword')

@cache_to_file_ttl_noc
def my_heavy_function(x):
    """Performs heavy computations"""
    print('Hi, I am called...')
    return x**2

my_heavy_function(2) # Will print 'Hi, I am called...'
my_heavy_function(2) # Will not print 'Hi, I am called...'

Calling the my_heavy_function function being decorated by cache_to_file_ttl_noc will store 4 (result of computations) in the file mycache.dat; along with the result of computations, additional info will be stored (these all will be encrypted by the RSA algo with the password mypassword): result expiration time (computed from ttl), noc and the number of performed calls of the decorated function (my_heavy_function). Data will not be encrypted, if pycrypto package isn’t installed. If you pass non- empty key parameter to the Cache constructor, the warning will occurred (“Pycrypto not installed. Data isn’t encrypted”); In this case, the cache will work without encryption functionality.

Testing

The code tested (and works as expected) in Python > 2.7.x and Python > 3.4.x.

python -m cachepy.tests

TODO

• Writing backend for redis server

• Testing in Python 3.x causes Error 11?!

Log list

• Version 0.1

  • initial release

Code author: Dmitry Kislov <[e-mail]>