PyCache

Object cache implementation in python

Dependency

All you need is python installed on your system and you are ready to go. However, you will need to install one python module - nose for testing.

easy_install nose

Running

from cache import Cache

#cache of entries size = 10
cache = Cache(size = 10)

#basic write operation
cache.write(key = "key1",value = "value1")
cache.write("key2", "value2")

#basic read operation
value =  cache.beginRead("key1")
print value

#doesn not return anything
cache.endRead("key1")

return

Or, just run

python cache.py

Testing

cd path/to/PyCache
nosetests

Notes

1. GIL in CPython

Though dictionary accesses are thread-safe in CPython due to Global Interpreter Lock, I have used a lock to protect dict to make this code implementation independent. http://effbot.org/pyfaq/what-kinds-of-global-value-mutation-are-thread-safe.htm

""" Write (key,value) into the cache """
with self.hash_db_lock:
	self.hash_db[key] = Elem(value)

2. Assumption of correct usage of endRead() function

Here, I have assumed that the application using this object cache will make a single call to endRead() corresponding to every beginRead() call.

Usage:

self.cache.write("test_key", "test_value")

print self.cache.beginRead("test_key")

self.cache.endRead("test_key")
self.cache.endRead("test_key") #Not allowed