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Don't mention __slots__ as a technique for error avoidance
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@ -424,14 +424,9 @@ Finally, it's possible to constrain the list of attributes that can be
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referenced on an object using the new \member{__slots__} class attribute.
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Python objects are usually very dynamic; at any time it's possible to
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define a new attribute on an instance by just doing
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\code{obj.new_attr=1}. This is flexible and convenient, but this
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flexibility can also lead to bugs, as when you meant to write
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\code{obj.template = 'a'} but made a typo and wrote
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\code{obj.templtae} by accident.
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A new-style class can define a class attribute named \member{__slots__}
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to constrain the list of legal attribute names. An example will make
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this clear:
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\code{obj.new_attr=1}. A new-style class can define a class attribute named
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\member{__slots__} to limit the legal attributes
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to a particular set of names. An example will make this clear:
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\begin{verbatim}
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>>> class C(object):
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@ -443,16 +438,17 @@ None
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>>> obj.template = 'Test'
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>>> print obj.template
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Test
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>>> obj.templtae = None
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>>> obj.newattr = None
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Traceback (most recent call last):
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File "<stdin>", line 1, in ?
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AttributeError: 'C' object has no attribute 'templtae'
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AttributeError: 'C' object has no attribute 'newattr'
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\end{verbatim}
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Note how you get an \exception{AttributeError} on the attempt to
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assign to an attribute not listed in \member{__slots__}.
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\subsection{Related Links}
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\label{sect-rellinks}
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