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37 lines
1.3 KiB
Python
37 lines
1.3 KiB
Python
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# extutil.py - useful utility methods for extensions
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#
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# Copyright 2016 Facebook
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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def replaceclass(container, classname):
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'''Replace a class with another in a module, and interpose it into
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the hierarchies of all loaded subclasses. This function is
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intended for use as a decorator.
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import mymodule
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@replaceclass(mymodule, 'myclass')
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class mysubclass(mymodule.myclass):
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def foo(self):
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f = super(mysubclass, self).foo()
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return f + ' bar'
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Existing instances of the class being replaced will not have their
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__class__ modified, so call this function before creating any
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objects of the target type.
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'''
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def wrap(cls):
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oldcls = getattr(container, classname)
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for subcls in oldcls.__subclasses__():
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if subcls is not cls:
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assert oldcls in subcls.__bases__
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newbases = [oldbase
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for oldbase in subcls.__bases__
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if oldbase != oldcls]
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newbases.append(cls)
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subcls.__bases__ = tuple(newbases)
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setattr(container, classname, cls)
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return cls
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return wrap
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