Any problems with *lots* of attributes?

[Aahz]

In article <246a4e07.0402042327.5192034a at posting.google.com>,
Frank Millman <frank at chagford.com> wrote:
>Aahz <aahz at pythoncraft.com> wrote:
>> 
>> OTOH, there's certainly nothing wrong with using dicts; they are the
>> single most fundamental Python data type after strings.  (All Python
>> name/attribute access is built on top of dicts.)
>
>This is exactly my point, but I may be misunderstanding how it works
>internally. If I have a class with 20 attributes, it will have a
>dictionary with 20 entries. If I have hundreds of instances of the
>class, do I end up with hundreds of dictionaries (or the equivalent
>internal structures), and if so, does this not lead to memory bloat?
>If I store the data in a list, there will only be one dictionary entry
>per instance. On the other hand, I suppose there must be some reference
>to each of the elements of each list, so maybe there is an equivalent
>overhead. Is this a valid concern, or am I worrying about nothing?

You're mostly worrying about nothing; your analysis is essentially
correct.

>    def getval_from_list(self):
>        start = time()
>        for i in xrange(1000000):
>            aa = self.l[0]
>        return (time() - start)

Try this instead:

    def getval_from_list(self):
        l = self.l
        start = time()
        for i in xrange(1000000):
            aa = l[0]
        return (time() - start)

Your original code pays the penalty for *both* dict/attribute lookup and
list lookup.
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

"The joy of coding Python should be in seeing short, concise, readable
classes that express a lot of action in a small amount of clear code -- 
not in reams of trivial code that bores the reader to death."  --GvR