Type-checking unpickled objects
I have this class, and I've been pickling it's objects as a file format for my program, which works great. The problems are a.) how to handle things when the user tries to load a non-pickled file, and b.) when they load a pickled file of the wrong class. a. I can handle with a general exception I guess. I just tried to pickle.load() a .pyc and it failed with a 'KeyError' exception - however that works. It might do that every time, it might not. Regarding b., if I type check I simply get the 'instance' type, which doesn't get me all of the way there because I might have an instance of the wrong class. I can't find any sort of __type__ attribute to set in the objects. Perhaps I should use __str__? -- http://mail.python.org/mailman/listinfo/python-list
Re: Type-checking unpickled objects
Gordon Airporte wrote: >I have this class, and I've been pickling it's objects as a file format > for my program, which works great. The problems are a.) how to handle > things when the user tries to load a non-pickled file, and b.) when they > load a pickled file of the wrong class. > > a. I can handle with a general exception I guess. I just tried to > pickle.load() a .pyc and it failed with a 'KeyError' exception - however > that works. It might do that every time, it might not. I hope you're aware of the fact that pickle is not suitable for applications where you cannot trust the source; see e.g. http://www.livejournal.com/users/jcalderone/15864.html (one of the comments show how to place restrictions on what can be loaded from a given pickle) > Regarding b., if I type check I simply get the 'instance' type, which > doesn't get me all of the way there because I might have an instance of > the wrong class. I can't find any sort of __type__ attribute to set in > the objects. Perhaps I should use __str__? how about a plain obj = cPickle.load(...) if not isinstance(obj, Class): print "expected a Class instance" -- http://mail.python.org/mailman/listinfo/python-list
Re: Type-checking unpickled objects
isinstance! Now why didn't I know about that? Thanks you. I guess I'll need a throwaway instance of the class to run type() on to get a usable type object for comparison, but I'll work something out. As to the security considerations...this is a small enough program with a limited enough release that I'm not going to sweat it, although I will keep this in mind. -- http://mail.python.org/mailman/listinfo/python-list
Re: Type-checking unpickled objects
> I guess I'll > need a throwaway instance of the class to run type() on to get a usable > type object for comparison, but I'll work something out. Never mind - I can just pass the name of the class, as it should be. -- http://mail.python.org/mailman/listinfo/python-list
