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I am trying to understand when to use __getattr__ or __getattribute__. The documentation mentions __getattribute__ applies to new-style classes. What are new-style classes?
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__getattribute__This method should return the (computed) attribute value or raise an AttributeError exception. In order to avoid infinite recursion in this method, its implementation should always call the base class method with the same name to access any attributes it needs, for example, object.
What is getattr() used for? Explanation: getattr(obj,name) is used to get the attribute of an object. 6.
The getattr() function returns the value of the specified attribute from the specified object.
__getattr__Called when an attribute lookup has not found the attribute in the usual places (i.e. it is not an instance attribute nor is it found in the class tree for self).
A key difference between __getattr__ and __getattribute__ is that __getattr__ is only invoked if the attribute wasn't found the usual ways. It's good for implementing a fallback for missing attributes, and is probably the one of two you want.
__getattribute__ is invoked before looking at the actual attributes on the object, and so can be tricky to implement correctly. You can end up in infinite recursions very easily.
New-style classes derive from object, old-style classes are those in Python 2.x with no explicit base class. But the distinction between old-style and new-style classes is not the important one when choosing between __getattr__ and __getattribute__.
You almost certainly want __getattr__.
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