Marc 'BlackJack' Rintsch wrote: > In <[EMAIL PROTECTED]>, crystalattice wrote: > > > On Mon, 31 Jul 2006 14:35:39 -1000, Simon Forman <[EMAIL PROTECTED]> > > wrote: > > > >> What kind of trouble were you having with pickle? > > > > It's mostly a combination of things (I hope you can follow my logic). > > First, to use "good programming practice", I want to implement a > > try/except block for opening the pickle file. But I can't figure out if > > this block should be included outside the classes, included in just the > > base class, or if the base and subclasses need it; I'm leaning to putting > > outside the classes as a global method. > > That's not a problem with pickle but where you think a potential IO error > is handled best. Ask yourself if you can do something sensible at the > point where you catch an exception. If you don't know what to do with it, > don't catch it and just let it propagate. > > > When pickling a class instance, is the pickle statement placed within the > > class (say, at the end of the class) or is it where the instance is > > created, such as a test() method? > > `pickle.dump()` and `pickle.load()` are not statements but just functions. > And you should place a call where you actually want to save or load > instances in your program flow. > > > Plus, to modify data in a class, do I have to unpickle the whole thing > > first or is there a way to modify the data while it's pickled? Actually, > > I think I can answer that last question: a character instance, having > > been created, will stay resident in memory until the player quits, > > character dies, or otherwise is no longer needed. At that point the > > character instance should be pickled (if necessary) to disk; pickle > > shouldn't be used while data modification is required and the class > > instance is "active", correct? > > Yes that's correct. It wouldn't be different with XML. > > > I also remember reading on a thread here that pickle sometimes has issues > > when used with classes, which makes me hesitant to pickle an entire class > > instance. That's why I thought XML may be safer/better. > > You can't pickle everything. Files for example are unpickleable and you > can't pickle code so pickling classes is not that useful. > > An advantage of `pickle` is that it's in the standard library and ready to > use for serialization. To get an XML solution you must either write your > own serialization code or use a 3rd party library. > > What are the problems you fear when using `shelve` by the way? > > Ciao, > Marc 'BlackJack' Rintsch The ideas I got about shelve are mostly due to this thread: http://tinyurl.com/lueok. There weren't any other threads contradicting the information so I figured it has merit. Actually, not many people seem to use shelve very much; pickle is used more often so I decided to give it a try and see how it works for me.
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