Backend DevelopmentPython TutorialWhen should you use `__getattr__` vs `__getattribute__` in Python?
getattr vs getattribute in Python
Understanding the distinction between __getattr__ and __getattribute__ is crucial when working with Python objects. Both methods are designed to control how attributes are retrieved from an object, but they perform different functions and have specific use cases.
New-Style Classes
Before delving into the differences between __getattr__ and __getattribute__, it's worth clarifying the concept of "new-style classes." In Python, there are two types of classes: new-style and old-style. New-style classes are those that inherit from the object class explicitly or implicitly, while old-style classes are those in Python 2.x that do not have a base class defined. However, this distinction is not relevant to the choice between __getattr__ and __getattribute__.
getattr vs getattribute
__getattr__ is invoked when an attribute is accessed that is not found in the object's dictionary or in any of its base classes. It allows you to implement a fallback mechanism for retrieving attributes that do not exist on the object itself. This method is commonly used to provide dynamic attribute access, such as in metaprogramming scenarios.
__getattribute__, on the other hand, is invoked when accessing any attribute on the object, regardless of whether it exists. It is called before the object's dictionary or base classes are checked. Implementing __getattribute__ can be tricky as it requires careful handling to prevent infinite recursion.
When to Use getattr or getattribute
To summarize, __getattr__ should be used when you want to handle attribute retrieval for missing attributes, providing a fallback mechanism. __getattribute__, while more versatile, can be more complex to implement correctly and is typically not necessary for most practical purposes.
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