Re: Are all classes new-style classes in 2.4+?

On Sun, 31 Dec 2006 03:57:04 -0800, Isaac Rodriguez wrote:

Hi,

This is probably a very basic question, but I've been playing with new
style classes, and I cannot see any difference in behavior when a
declare a class as:

class NewStyleClass(object):

or

class NewStyleClass:

I declare property members in both and it seems to work the exact same
way.

Then you aren't looking very closely. Try with a calculated property.

class New(object):
.... def __init__(self):
.... self._n = 1
.... def getter(self):
.... return "spam " * self._n
.... def setter(self, n):
.... self._n = n
.... spam = property(getter, setter, None, None)
....
obj = New()
obj.spam
'spam '
obj.spam = 3
obj.spam
'spam spam spam '
obj.spam = 7
obj.spam
'spam spam spam spam spam spam spam '

Now try with an old-style class.

class Old:
.... def __init__(self):
.... self._n = 1
.... def getter(self):
.... return "spam " * self._n
.... def setter(self, n):
.... self._n = n
.... spam = property(getter, setter, None, None)
....
obj = Old()
obj.spam
'spam '
obj.spam = 3
obj.spam
3

Properties should not be used with old-style classes because they just
don't work correctly.



--
Steven.

.

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