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https://issues.apache.org/jira/browse/QPID-4015?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Justin Ross updated QPID-4015:
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Labels: patch (was: )
> qpid.packer.Packer implements abstract methods incorrectly.
> -----------------------------------------------------------
>
> Key: QPID-4015
> URL: https://issues.apache.org/jira/browse/QPID-4015
> Project: Qpid
> Issue Type: Improvement
> Components: Python Client
> Reporter: Tim Sally
> Priority: Minor
> Labels: patch
> Attachments:
> 0001-Use-abstract-base-class-to-implement-qpid.packer.Pac.patch
>
>
> qpid.packer.Packer implements abstract methods incorrectly. Specifically, it
> uses the method suggested [here|http://norvig.com/python-iaq.html]. When an
> abstract method is called, the invalid name _abstract_ results in a NameError
> exception. The merits of this approach, along with the other most common
> approaches, are summarized in the table below
> ||Method||||Stops Execution||Stops Execution at Object Creation||Sensible
> Exception Name||
> |_abstract_ keyword|yes|no|no|
> |raise NotImplementedError|yes|no|yes|
> |Abstract Base Classes|yes|yes|yes|
> Using _abstract_ is not preferable because a NameError does not make
> immediately clear what is going on. Raising a _NotImplementedError_ exception
> is a great alternative because the exception name is logical. However, even
> better is the use of Abstract Base Classes (ABCs). ABCs raise an exception at
> object instantiation, whereas the other two methods do not result in an
> exception until an abstract method is called.
> As an example, consider qpid.codec010.Codec. It is not immediately clear this
> class should not be used. And indeed, it is not used anywhere. Rather,
> qpid.codec010.StringCodec is the only class in qpid.codec010 meant to be used
> directly. Using an abstract base class prevents qpid.codec010.Codec objects
> from being created.
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