What is MRO in Python?
MRO, an acronym for Method Resolution Order is a concept majorly used in inheritance and multiple inheritance in Python. It is the order in which a method is searched for in a class hierarchy. We have what we call a simple inheritance where a child class only inherits from a single parent class, this is a very familiar type of inheritance and it is also very simple and quite straightforward but then what happens when we have more than one parent class and child class?. Firstly, lets take a look at the various types of inheritance. Python has many types of inheritance. These types are based on the number of parents and child classes as well as the hierarchical order of the classes. There are broadly five types of inheritance. The first type is called a simple inheritance where we have a single parent and a single child class. The second type of inheritance is the multiple inheritance which involves a child class inheriting from more than one parent. The third type of inheritance is the multi – level inheritance which takes place on several levels. The fourth type of inheritance is the hierarchical inheritance which concerns how several sub classes inherit from a common parent. The last type of inheritance is the hybrid inheritance which mixes the characteristics of the other four types of inheritance.
As these inheritance types demonstrate, inheritance becomes increasingly complex and more independent as the number of classes in a project grow. So how do developers know which classes inherit from which? With the use of MRO, developers can determine the order in which Python will search for methods. MRO will help determine the order in which a given method or attribute is passed through in a search of the hierarchy of classes from where it belongs. In OOP in Python, the MRO determines the order in which a method is searched for in a class hierarchy. It is especially useful in Python because it supports multiple inheritance meaning that a class can inherit from multiple parent classes.
How do you get the MRO of an object in Python?
The MRO can be accessed using the _mro_ attribute on a class or by using the mro() method. By examining the MRO, you can see the order in which Python will search for methods.
C3 Linearization Algorithm
Python calculates the MRO using the C3 Linearization Algorithm. This algorithm follows monotonicity, which broadly means that an inherited property cannot skip over direct parent class. The algorithm also follows the inheritance graph of the class and the super class is visited only after visiting the methods of the local class. So by following the C3 Linearization Algorithm, Python ensures a predictable and consistent order of method resolution.
Conclusion
In conclusion, it is very crucial for developers to understand how the Method Resolution Order(MRO) works as it is very effective when working with inheritance and multiple inheritance in Python. By making use of MRO, you can anticipate and predict how methods will be searched and executed in a class hierarchy. So as a Python Developer, you need to understand the concept of MRO and how you can effectively implement it in your code so as to achieve a neat and concise working environment.
