Classes and Methods in Python - Essay Example

Chapter 17 es and methods Object-Oriented features Object-oriented language is a language that uses method syntax and user-defined classes, to facilitate object-oriented programming. Object-oriented programming on the other hand is a style of programming where data and operations that operate it are arranged into classes and methods. (http://thinkpython.com)

Method Refers to a function of a class. Semantically, methods are the same as functions though there are two major syntactic differences. They are Methods usually defined inside a class to make the relationship between class and method explicitly. The syntax for invoking a method is for much different from the syntax for calling a function. Subject refers to the object a method is invoked on. .(http://en.wikipedia.org)Printing objects Example:class Time(object): """Represents the time of day.

""" def print_time(time): print %.2d:%.2d:%.2d % (time.hr, time.min, time.sec) For this function to display time, an argument ‘time’ must be evoked to the object.>>> start = Time () >>> start.hour = 9 >>> start.minute = 45 >>> start.second = 00 >>> print_time (start) 09:45:00 To make a function a method, one has to move function definition inside the class definition.class Time(object): def print_time(time): print %.2d:%.2d:%.2d % (time.hr, time.min, time.sec)Ways of representing a methoda) Use of function syntax- uses dot notation>>> Time.

print_time(start) 09:45:00In this the time represents class and print_time is the name of the method. The start is the argument invoked to the object as a parameter. .(http://en.wikipedia.org)b) Use of method syntax- also uses dot notation>>> start.print_time() 09:45:00In this, print_time is the method and start is the object that the method is invoked on which is called the subject. The init MethodInti means initialization. It is usually a method that is invoked when the object is instantiated. When you press to print an object python invokes the str method outcome:>>> time = Time(9, 45) >>> print time 09:45:00Operator overloading This refers to changing the behavior of an operator so that its works with user-defined types. Operators in python usually have a corresponding special method like _add_.

It involves changing the behavior of an operator like + so it works with a user-defined type. (http://en.wikipedia.org)Other definitions: Time-based dispatch is a pattern in programming that is used to check the type of an operand and usually, it invokes different functions for different types. Polymorphism Refers to a process where an object can be used for more than one function. Functions that can work with several types are said to be polymorphic.DebuggingInterface and implementation goal of object-oriented design is to ensure the software is more maintainable.

To achieve this goal is to keep interfaces separate from implementations and this means that you have to hide the attributes. This principle is called Information hiding.