[Python-bugs-list] [ python-Bugs-612071 ] __slots__ ignored in derived classes

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Bugs item #612071, was opened at 2002-09-20 11:18
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=612071&group_id=5470

Category: Type/class unification
Group: Python 2.2.1
Status: Open
Resolution: None
Priority: 5
Submitted By: Yakov Markovitch (markovitch)
Assigned to: Nobody/Anonymous (nobody)
Summary: __slots__ ignored in derived classes

Initial Comment:
If some class is based on another new-style class and
defines __slots__, and the base class has no __slots__
definition, __slots__ in derived class completely ignored.

E.g.:

class A(object):
    pass

class B(A):
    __slots__ = ['a']

b = B()
b.a = 1
b.b = 2
print b.a, b.b

The code above serenely prints  
1 2

On the other hand, 

class A(object):
    __slots__ = []

class B(A):
    __slots__ = ['a']

b = B()
b.a = 1
b.b = 2
print b.a, b.b

raises AttributeError:
AttributeError: 'B' object has no attribute 'b'
which is correct.


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