![Why do we need classes?
• Which field contains what type of information?
client = [“xxxxxxxxxxxxxxx",
“0000000000",
“xxxxxxxxx",
0]
The parts of a composite list can
be accessed via [index] but they
cannot be labeled (what do these
fields store?)
This isn’t immediately clear from looking at the program statements.](https://image.slidesharecdn.com/1-250413043657-305d5571/85/Introduction-to-Object-Oriented-Programming-in-Python-pptx-3-320.jpg)
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Introduction to Object Oriented Programming in Python.pptx
- 1. OOP in Python A brief overview CS 357 Dr. Eduardo Ceh
- 2. Topics • Why do we need classes? • Defining Classes • Defining Objects • Class variables vs Instance variables • Methods • Inheritance • Polymorphism
- 3. Why do we need classes? • Which field contains what type of information? client = [“xxxxxxxxxxxxxxx", “0000000000", “xxxxxxxxx", 0] The parts of a composite list can be accessed via [index] but they cannot be labeled (what do these fields store?) This isn’t immediately clear from looking at the program statements.
- 4. Object-Oriented Programming You have learned structured programming Breaking tasks into subtasks Writing re-usable methods to handle tasks We will now study Objects and Classes To build larger and more complex programs To model objects we use in the world A class describes objects with the same behavior. For example, a Car class describes all passenger vehicles that have a certain capacity and shape.
- 5. A class class In OOP a class is the definition of an object. In Python we define classes. You can consider a class as a blueprint of an object Using a class you instantiate objects These objects belong to the same class and therefore they contain the same characteristics specified in the class instances objects
- 7. Diagram of a Class Private Data We assume each object has its own private data that other objects cannot directly access Methods of the public interface provide access to private data, while hiding implementation details: This is called Encapsulation (Python has a loose definition of this) Public Interface Each object has a set of methods available for other objects to use Class Private Data (Variables/Attributes) Public Interface (Methods) Variables “must” be private Methods must be public By the way, this is a class diagram
- 8. Let’s go to Google Colab • Topics: • Classes • Writing classes in Python • Class variables • Class constructor • Instance variables • Instance methods • Combining Class variables and Instance variables • Class inheritance and Polymorphism • Inheritance • Polymorphism
- 9. Importing your classes as modules • To use any package in your code, you must first make it accessible. • You need to tell python to first import a module in your code so that you can use it. • If you have your own python files you want to import, you can use the import statement as follows: import my_file # assuming you have the file, my_file.py in the current directory. # For files in other directories, provide path to that file, absolute or relative.
- 10. Importing our Python class The file we want to import Having the class Client
- 11. Importing our Python class The file where we want to use the Class The output if we run the main.py Something is NOT right.
- 12. __name__ == “__main__” Magic method that allows or prevents parts of code from being run when the modules are imported When the Python interpreter reads a file, the __name__ variable is set as __main__ if the module being run, or as the module's name if it is imported.
- 13. Importing our Python class Now, the code in client.py that is not part of the class is not executed.
- 14. Importing elements from the file File Class
Editor's Notes
- #4: It is difficult to understand and update a program that consists of a large collection of methods. To overcome this problem, computer scientists invented object-oriented programming, tasks are solved by collaborating objects When you develop an object-oriented program, you create your own objects that describe what is important in your application.
- #14: If you only use “import Client”, you are importing EVERYTHING from that file. Therefore, you need to specify what classes or methods you want to use. For example, Client.Client()