eb303
3/4/2010 1:21:00 PM
On Mar 3, 6:41 pm, Laszlo Nagy <gand...@shopzeus.com> wrote:
> 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
Seems you try to reinvent functools:
class GdbmCacheStorage(object):
def __init__(self,basedir,basename):
...
cache_factory = functools.partial(GdbmCacheStorage, "~gandalf/db",
"test")
print cache_factory()
Is it what you're after? I didn't see the point in creating a "cached
factory" for MemoryCacheStorage though, since it has no constructor
parameters to cache anyway. So doing 'cache_factory =
MemoryCacheStorage' in your example would do exactly the same thing as
what you did.
HTH
- Eric -