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Other implementations are possible: for example, objects in Python use associative key-value containers. [4] Some programming languages such as Eiffel support specification of invariants as part of the definition of the class, and enforce them through the type system.
Python supports most object oriented programming (OOP) techniques. It allows polymorphism, not only within a class hierarchy but also by duck typing. Any object can be used for any type, and it will work so long as it has the proper methods and attributes. And everything in Python is an object, including classes, functions, numbers and modules.
Python allows programmers to define their own types using classes, most often used for object-oriented programming. New instances of classes are constructed by calling the class (for example, SpamClass or EggsClass ()), and the classes are instances of the metaclass type (itself an instance of itself), allowing metaprogramming and reflection.
For example, instead of inheriting from class Person, class Employee could give each Employee object an internal Person object, which it then has the opportunity to hide from external code even if class Person has many public attributes or methods. Delegation is another language feature that can be used as an alternative to inheritance.
The Decorator Pattern (or an implementation of this design pattern in Python - as the above example) should not be confused with Python Decorators, a language feature of Python. They are different things. Second to the Python Wiki: The Decorator Pattern is a pattern described in the Design Patterns Book.
According to Design Patterns: Elements of Reusable Object-Oriented Software: "Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory method lets a class defer instantiation to subclasses." [2] Creating an object often requires complex processes not appropriate to include within a composing object.
In object-oriented programming, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance. It is one of the well-known "Gang of Four" design patterns , which describe how to solve recurring problems in object-oriented software. [ 1 ]
If a third-party library implements a class that cannot be modified, a client cannot use an instance of it with an interface unknown to that library even if the class satisfies the interface requirements. A common solution to this problem is the adapter pattern. In contrast, with duck typing, the object would be accepted directly without the ...