This is just an interesting code pattern that I have recently used:
class CacheStorage(object):
"""Generic cache storage class."""
@classmethod
def get_factory(cls,*args,**kwargs):
"""Create factory for a given set of cache storage creation
parameters."""
class CacheStorageFactory(cls):
_construct_args = args
_construct_kwargs = kwargs
def __init__(self):
cls.__init__(self,
*self._construct_args,**self._construct_kwargs)
return CacheStorageFactory
Then, I can create subclasses like:
class GdbmCacheStorage(CacheStorage):
"""Gdbm cache storage class.
@param basedir: Base directory where gdbm files should be stored.
@param basename: Base name for logging and creating gdbm files.
"""
def __init__(self,basedir,basename):
..... blablabla place initialization code here
class MemoryCacheStorage(CacheStorage):
"""In-Memory cache storage class.
Please note that keys and values are always mashal-ed.
E.g. when you cache an object, it makes a deep copy.
"""
def __init__(self):
..... blablabla place initialization code here
And the finally, I can create a factory that can create cache storage
instances for storing data in gdbm in a given directory:
cache_factory = GdbmCacheStorage.get_factory("~gandalf/db","test")
print cache_factory # <class '__main__.CacheStorageFactory'>
print cache_factory()
OR I can create a factory that can create instances for storing data in
memory:
cache_factory = MemoryCacheStorage.get_factory()
print cache_factory # <class '__main__.CacheStorageFactory'>
print cache_factory() # <__main__.CacheStorageFactory object at 0x8250c6c>
Now, here is my question. Am I right in doing this? Or are there better
language tools to be used in Python for the same thing? This whole thing
about creating factories looks a bit odd for me. Is it Pythonic enough?
Thanks,
Laszlo
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