.. include:: global.rst

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12: Single Inheritance
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Summary
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- Inheritance is at its most basic about code reuse
- OOP has a number of different philosophies that attempt to motivate its use.
    - The most common is that classes should model the real world - the domain model
- The domain model has to be hierarchial because single inheritance creates class hierarchies; the problem is that the world isn't a simple hierarchy
- The four pillars of OOP are classes, inheritance, encapsulation, and polymorphism
- Python allows multiple inheritance, but you can restrict your use of it to single inheritance if you want to
- Inheritance in Python is a simple extension of the way attributes are resolved
    - First the instance class is created, then the class, then the base class, and then its base class, and so on until the attribute is located
- Attributes can be overridden by simplify defining them in the class that inherits
- The super() built-in function can be used to return an attribute from the first class in the inheritance chain to define it
- The inheritance chain is defined in the class's __mro__ attribute
- super() works by searching the __mro__ for the first class to define the method
    - You can specify the class that has the __mro__ to use and the starting class for the search
- If you restrict yourself to single inheritance you can dispense with super() and access the attribute directly, but with multiple inheritance this simple approach doesn't work
- Metaclasses can also be a part of an inheritance chain and there are rules for which metaclass is used.

Program
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.. literalinclude:: programs/chapterTwelve.py
   :language: python

Program Output
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.. code-block:: console