"Alex Gusarov" <al************@gmail.comwrites:
> class Event(object):
Always subclass object, unless you have a very compelling reason not to,
or you are subclassing something else.
I've thought that if I write
class Event:
pass
, it'll be subclass of object too, I was wrong?
You are wrong for Python 2.X, but right for Python 3 where old-style
classes are gone for good.
What you define with the statement
class Event: pass
is an 'old-style' class. Witness:
>>class Event: pass
...
>>class NewEvent(object): pass
...
>>type(Event)
<type 'classobj'>
>>type(NewEvent)
<type 'type'>
>>type(Event())
<type 'instance'>
del>>type(NewEvent())
<class '__main__.NewEvent'>
All old-style classes are actually objects of type 'classobj' (they
all have the same type!), all their instances are all of type 'instance'.
>>type(FooBar) == type(Event)
True
>>type(FooBar()) == type(Event())
True
Whereas instances of new-style classes are of type their class:
>>class NewFooBar(object): pass
...
>>type(NewFooBar) == type(NewEvent)
True
>>type(NewFooBar()) == type(NewEvent())
False
However, in python 2.X (X 2?), you can force all classes to of a
certain type by setting the global variable '__metaclass__'. So:
>>type(Event) # Event is an old-style class
<type 'classobj'>
>>__metaclass__ = type
class Event: pass
...
>>type(Event) # Now Event is new-style!
<type 'type'>
HTH
--
Arnaud
