Python Classes and Objects

Al-Zaytoonah Private University of Jordan

Lab Manual Overview

• The lab manual is designed to teach students about Object-Oriented Paradigm (OOP) using Python.
• Students will learn about encapsulation, inheritance, and polymorphism.

Required Tools and Resources

• Pycharm is the required tool.

Rules and Policies

• Rules for lab sessions:
  • Attend lab sessions on time.
  • Bring your notebook and laptop.
  • No food or beverages allowed in the lab.
  • Interact with lab supervisors and ask questions.
  • Maintain silence and discipline.
  • Log in to your computer using your student account.
  • Complete lab exercises.
  • Clean up after lab sessions.
• Attendance policy:
  • Attendance is required.
  • Absence from lab sessions is recorded.
  • Absence warning system is in place.
• Grading policy:
  • Lab supervisor records progress during lab sessions.
  • Assignments are submitted.
  • Final lab grade is based on overall performance.

Learning Outcomes

• ILO1-k: Understand advanced topics in object-oriented programming in Python.
• ILO2-k: Knowledge of Python programming language structure and model.
• ILO3-s: Ability to use Python libraries for artificial intelligence and machine learning.
• ILO4-s: Write Python programs using NumPy, matplotlib, and pandas.
• ILO5-c: Implement programs using OOP concepts.
• ILO6-c: Write programs using common libraries for AI.

Exercise 1: Python Classes and Objects

• Class definition syntax: class class_name: ...
• Attributes are variables that belong to a class.
• Attributes are public and can be accessed using the dot (.) operator.
• ClassDocstring: a brief description of the class.
• Creating an object: my_object = MyClass()
• State, behavior, and identity of an object: example of a class Dog.

Exercise 2: The __init__() Function, The self Parameter, and The __str__() Function

• Method: a function associated with an object.
• self is a pointer to the current object.
• __init__() function: initializes the object's attributes.
• __str__() function: returns a string representation of the object.
• Experiment 1: creating a Person class with __init__() and myfunc() methods.
• Experiment 2: using the __str__() function.
• Experiment 3: using mysillyobject and abc instead of self.

Exercise 3: Accessing Attributes and Methods

• Attributes and methods are accessed using the dot (.) operator.
• Modifying properties on objects: my_object.age = 40
• Deleting object properties: del my_object.age
• Deleting objects: del my_object
• The pass statement: when a class definition has no content.

Exercise 4: Python Inheritance

• Inheritance: a class that inherits all the methods and properties from another class.
• Parent class: the class being inherited from.
• Child class: the class that inherits from another class.
• Syntax: class ChildClass(ParentClass): ...
• Experiment 1: creating a Person class and a Student class that inherits from Person.
• Experiment 2: using the super() function.
• Experiment 3: adding properties and methods to the Student class.

Exercise 5: Different types of Python Inheritance

• Single inheritance: a child class inherits from only one parent class.
• Multiple inheritances: a child class inherits from multiple parent classes.
• Multilevel inheritance: a child class inherits from a parent class that inherits from another class.
• Hierarchical inheritance: more than one derived class is created from a single base class.
• Hybrid inheritance: a combination of multiple types of inheritance.

Exercise 6: Python Polymorphism:1

• Polymorphism: methods/functions/operators with the same name that can be executed on many objects or classes.
• Class polymorphism: methods with the same name in different classes.
• Experiment 1: different classes with the same method: Car, Boat, and Plane classes with move() methods.
• Experiment 2: inheritance class polymorphism.### Classes and Objects
• A class called Vehicle can be created with child classes Car, Boat, and Plane that inherit its properties and methods.
• The Car class can be empty, but it still inherits brand, model, and move() from Vehicle.
• The Boat and Plane classes also inherit brand, model, and move() from Vehicle, but they override the move() method.
• Polymorphism allows for executing the same method for all classes, even if they have different implementations.

Polymorphism

• Polymorphism is the ability of an object to take on multiple forms.
• It allows for different classes to respond to the same method call.
• Polymorphism can be achieved through method overriding, where a child class provides a different implementation of a method inherited from its parent class.

Operator Overloading

• Operator overloading is a type of polymorphism where the same operator performs different operations depending on the operands.
• Examples of operator overloading include:
  • The + operator, which can be used for arithmetic addition, string concatenation, or list extension.
  • The * operator, which can be used for multiplication or string repetition.

File Handling

• The open() function is used to create a new file or open an existing file.
• The open() function takes two parameters: the filename and the mode (e.g., r for read, w for write, a for append, x for create).
• The open() function can be used with various modes, such as r for reading, w for writing, and a for appending.
• The close() function is used to close a file.

Encapsulation

• Encapsulation is the concept of hiding the implementation details of an object from the outside world.
• Encapsulation is achieved through the use of private and public members.
• Private members are denoted by a single underscore (_) and can only be accessed within the class.
• Public members are denoted by no underscore and can be accessed from outside the class.
• Getter and setter methods are used to access and modify private members.
• The @property decorator is used to define a getter method.
• The @property_name.setter decorator is used to define a setter method.

Abstraction

• Abstraction is the concept of showing only the necessary information to the outside world while hiding the implementation details.
• Abstraction is achieved through the use of abstract classes and interfaces.
• An abstract class is a class that cannot be instantiated and is used as a base class for other classes.
• An abstract class must have at least one abstract method.
• An abstract method is a method that is declared but not implemented.
• A concrete class is a class that provides an implementation for all the abstract methods of its parent class.

NumPy Modules

• NumPy is a Python library used for working with arrays.
• NumPy is used to provide an array object that is up to 50x faster than traditional Python lists.
• The array object in NumPy is called ndarray.
• NumPy can be installed using pip: pip install numpy.
• NumPy can be imported using import numpy as np.
• NumPy arrays can be created using the array() function.
• NumPy arrays can be 0-D, 1-D, 2-D, or 3-D.
• The ndim attribute returns the number of dimensions of a NumPy array.
• Array indexing is used to access elements of a NumPy array.
• Accessing elements of a 2-D or 3-D array requires using comma-separated integers representing the dimension and the index of the element.Here are the study notes in detailed bullet points:
• Experiment #14: Accessing the third element of the second array of the first array*
• Use arr[0, 1, 2] to access the third element of the second array of the first array
• The first number represents the first dimension, which contains two arrays
• The second number represents the second dimension, which also contains two arrays
• The third number represents the third dimension, which contains three values
• Negative Indexing*
• Use negative indexing to access an array from the end
• Example: arr[1, -1] returns the last element of the 2nd dimension
• NumPy Array Slicing*
• Slicing in Python means taking elements from one given index to another given index
• Use [*start*:*end*] to specify the range
• Use [*start*:*end*:*step*] to specify the step
• If you don't pass start, it's considered 0
• If you don't pass end, it's considered the length of the array in that dimension
• If you don't pass step, it's considered 1
• Experiment #1-#8: Array Slicing*
• Examples of slicing:
  • arr[1:5] returns elements from index 1 to 5 (excluding 5)
  • arr[4:] returns elements from index 4 to the end
  • arr[:4] returns elements from the beginning to index 4 (excluding 4)
  • arr[1:5:2] returns every other element from index 1 to 5 (excluding 5)
• Generate Random Number*
• Use from numpy import random to work with random numbers
• Example: x = random.randint(100) generates a random integer from 0 to 100
• Pandas Tutorial*
• Pandas is a Python library for data analysis
• Pandas can:
  • Analyze data
  • Delete rows that are not relevant or contain wrong values
  • Clean data
• The source code for Pandas is located on GitHub
• Experiment #1-#10: Pandas*
• Examples of using Pandas:
  • Creating a DataFrame from a dictionary
  • Creating a Series from a list
  • Adding labels to a DataFrame
  • Locating rows and columns in a DataFrame
  • Loading files into a DataFrame
  • Plotting data using Matplotlib
• Matplotlib*
• Matplotlib is a low-level graph plotting library in Python
• Matplotlib is used for visualization
• Examples of using Matplotlib:
  • Plotting x and y points
  • Plotting without lines
  • Using markers (e.g., 'o' for circle, '*' for star)
  • Using formats (e.g., 'o:r' for circle marker with red color)
  • Setting marker size and color
  • Setting line style and color
  • Using hexadecimal color values and color names