Thus spake Bart Cramer: > I have a question... : > > >>> class A: pass > ... > >>> class B(object) : pass > ... > >>> dir(A) > ['__doc__', '__module__'] > >>> dir(B) > ['__class__', '__delattr__', '__dict__', '__doc__', '__getattribute__', > '__hash__', '__init__', '__module__', '__new__', '__reduce__', > '__reduce_ex__', '__repr__', '__setattr__', '__str__', '__weakref__'] > > What is the difference between classes A and B? The funny thing is, when I > put these things into an array of length, say, a million, it turns out > that > class A eats about 184 bytes per instantiation, and class B a lot less > (sic!): plm 50 bytes. How come? >
class B is a "new-style' class, meaning that it inherits from a base, pre-existing class (in this case "object", which is as basic and generic as you can get!). class A has to start from nothing, which is why it consumes more memory yet has less functionality. (As a very, very rough analogy, imagine that you have thirty seconds to paint a sign. Which would be more efficient - freehand or a stencil? Given time, you can achieve more artistic results freehand, but the stencil gets you quick results.) As I understand it, in Python 3000 (aka 3.0), new-style classes will be mandatory. As you can already see, they give you more bang for the buck, so you might as well get used to using them now! -- www.fsrtechnologies.com
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