classes vs dicts

[David MacQuigg]

Excellent!  Someday, I hope to be smart enough I can see such a simple
solution right away.

-- Dave MacQuigg

On Thu, 13 May 2004 10:33:09 -0600, "Dave Brueck"
<dave at pythonapocrypha.com> wrote:

>David wrote:
>> My problem is similar, with the additional requirement that I need a
>> convenient way to access data deep within a hierarchy of parameters.
>> I chose classes over dictionaries because the syntax to access items
>> in a deeply nested dictionary is awkward.
>>
>> dict[window1][plot2][xaxis][label][font][size] = 12
>>
>> vs
>>
>> statefiles.window1.plot2.xaxis.label.font.size = 12
>>
>> The problem is I can't easily save the whole hierarchy to disk.
>> Pickle doesn't work with classes.  Also, I worry about the overhead of
>> classes when I am just needing a simple container.  A typical
>> statefile will have 1000 parameters in 300 classes nested up to ten
>> levels deep.  As a structure of nested classes this takes about 74KB
>> on disk.  Importing the file creates a .pyc file that is 157KB !!  It
>> does seem to import quickly, however, so speed may not be a problem.
>>
>> Seems like Python could use a "container" structure which would be
>> like a class, but without the overhead and with the ability to
>> "pickle" the whole structure.
>
>Forgive me if I don't understand the problem, but why can't you just do:
>
>class Bag:
>    def __init__(self, **kwargs):
>        self.__dict__.update(kwargs)
>
>Then if your data is like:
>
>settings
>    network
>        ip = '10.20.30.40'
>        port = 1234
>    logging
>        level = 3
>
>you would construct it by hand like:
>
>settings = Bag(network=Bag(ip='10.20.30.40', port=1234), logging=Bag(level=3))
>
>and you can access members like:
>
>print settings.network.ip
>or
>settings.network.useSSL = 1
>etc.
>
>and you can easily pickle _instances_ so persistence isn't really a problem:
>
>from cPickle import dumps, loads
>q = dumps(settings)
>newSettings = loads(q)
>
>Unless I'm misunderstanding the problem, the only remaining issue is the
>overhead. If that really is a problem (most likely not, but maybe if you're
>transferring it over a slow network connection or something), then simply use
>the built-in gzip or bz2 modules.
>
>-Dave
>