On Tue, 09 Jan 2018 11:28:03 +0200, Frank Millman wrote: > I have a class call Context containing only data, not methods. Instances > are passed around a lot in my application, with various methods > accessing various attributes.
That contradicts itself... your Context class has data, but no methods, and yet it has methods accessing various attributes? If you have a class with only data, and you access the attributes via the instance's __dict__, why not use an ordinary dict? Alternatively, use a SimpleNamespace: py> from types import SimpleNamespace py> bag = SimpleNamespace() py> bag.spam = 1 py> bag.eggs = 2 py> bag namespace(eggs=2, spam=1) > I wanted to allow various parts of my app to 'piggy back' on this by > adding their own attributes at certain points, to be read back at > various other points. [...] > To tidy this up, I changed it to allow other parts of the app to store > attributes directly into Context. To protect my 'core' attributes, I > made them read-only, using @property. This all works quite well. Except it is no longer a class with data and no methods. > Now I have a situation where various processes are 'long-running', and I > need to persist the data to disk so that it can be recovered in the > event of a crash. I want to use Json to store the data as a dictionary. > However, I have no idea which additional attributes have been added by > other parts of the application. Does it have to be JSON? If this is just for your own use, pickle will probably do what you want: py> import pickle py> class Foo: ... pass ... py> x = Foo() py> x.spam = 1 py> s = pickle.dumps(x) py> y = pickle.loads(s) py> y.spam 1 (Warning: pickle is not secure if arbitrary, untrusted users have write- access to the pickle files.) -- Steve -- https://mail.python.org/mailman/listinfo/python-list
