Python’s __getattribute__() Method

in

Today we’re going to talk about one of the most underrated and underutilized features in Python: __getattribute__. Now, before you start yawning and scrolling away, let me tell you that this method is not just some fancy name for a function. It’s actually pretty ***** useful!

So what exactly does it do? Well, when you call an attribute on an object in Python (like my_obj.attr), the interpreter first checks if there’s a direct match between attr and one of the object’s attributes. If not, it looks for a special method called __getattribute__() that can handle this case.

Now, you might be wondering: “Why would I ever need to use __getattribute__? Can’t I just access my object’s attributes directly?” And the answer is… sometimes! But there are situations where it’s more convenient or necessary to have a custom implementation for attribute access. For example, let’s say you want to create an object that can handle dynamic attributes based on user input.

Here’s some code to illustrate this:

# This is a class called DynamicObject that inherits from the object class
class DynamicObject(object):
    # This is the constructor method that initializes the object
    def __init__(self):
        # This sets the object's __dict__ attribute to an empty dictionary
        self.__dict__ = {}
        
    # This is a method that is called when an attribute is accessed
    def __getattribute__(self, attr):
        # This checks if the object has a __dict__ attribute and if the attribute being accessed is in the dictionary
        if hasattr(self, '__dict__') and attr in self.__dict__.keys():
            # If the attribute is in the dictionary, it returns the value of the attribute
            return object.__getattribute__(self, attr)
        else:
            # If the attribute is not in the dictionary, it raises an AttributeError
            raise AttributeError("'DynamicObject' object has no attribute '%s'" % (attr))
        
    # This is a method that allows for the setting of dynamic attributes
    def set_dynamic_attr(self, key, value):
        # This adds the key-value pair to the object's __dict__ attribute
        self.__dict__[key] = value

In this example, we have a DynamicObject class that can dynamically add and remove attributes based on user input. When you call an attribute that doesn’t exist directly (like my_obj.foo), the __getattribute__() method is called instead of raising an AttributeError. If the attribute exists in our internal dictionary, it returns the value; otherwise, it raises a custom error message.

Now, some people might argue that this is not very Pythonic and goes against the spirit of the language. And they’re right! But sometimes you need to bend the rules for practicality or performance reasons. In fact, many popular libraries in Python use __getattribute__() internally (like numpy) to optimize attribute access on large datasets.

If you want to learn more about this topic, I highly recommend checking out the official documentation or some of the great resources available online (like RealPython). And if you have any questions or comments, feel free to leave them below. Later!

SICORPS