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Showing content from https://realpython.com/ref/builtin-exceptions/attributeerror/ below:

Python’s Built-in Exceptions – Real Python

AttributeError is a built-in exception that occurs when you attempt to access a method or attribute that isn’t defined for the object in question.

You should handle this exception to ensure your code doesn’t crash. Catching an AttributeError allows you to provide a graceful degradation or alternative solution when users try to access an attribute that’s missing.

• Accessing a method or attribute that doesn’t exist in a class or module
• Using the wrong attribute name due to a typo
• Accessing an attribute that was supposed to be dynamically added but hasn’t been initialized yet
• Attempting to access attributes on a NoneType object due to uninitialized or improperly assigned variables

You should handle this exception to ensure your code doesn’t crash. Catching an AttributeError allows you to provide a graceful degradation or alternative solution when users try to access a missing attribute.

An example of when the exception appears:

An example of how to handle the exception:

Every Python object will raise an AttributeError when you attempt to access a non-existent attribute on it. When you need to implement custom logic, then you can edit .__getattr__() accordingly before raising the error manually:

You could also provide fallback mechanisms for the lookup before raising the AttributeError. Raising it manually also allows you to customize the error message.

For example, say that you have a Pen class with a .color attribute:

The class works correctly with .color but fails with .colour. To fix the above code, you could customize the attribute lookup in .__getattr__() before raising AttributeError manually:

With these edits to Pen, you users can now access the ._color attribute with both .color and .colour:

At the same time, the class still raises an AttributeError when you try to access a non-existent attribute.

Note that you need to manually raise AttributeError in .__getattr__() if you overwrite the default implementation with your custom logic. Otherwise, you break the default behavior of raising an AttributeError when looking up a non-existent attribute.

For additional information on related topics, take a look at the following resources:

• Python's Magic Methods: Leverage Their Power in Your Classes (Tutorial)
• Working With Python's Built-in Exceptions (Course)
• Python's Built-in Exceptions: A Walkthrough With Examples (Quiz)
• Python's Magic Methods in Classes (Course)
• Python's Magic Methods: Leverage Their Power in Your Classes (Quiz)

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