How to create a list of objects in a Python class

Python is a dynamic and technology-savvy programming language that supports object-oriented programming (OOP). At the core of OOP is the concept of objects, which are instances of classes. In Python, classes serve as blueprints for creating objects with specific properties and methods. A common use case in OOP is to create a list of objects, where each object represents a unique instance of a class.

In this article, we will discuss the process of creating a list of objects in a Python class. We'll discuss the basic steps involved, including defining a class, creating objects of that class, adding them to a list, and performing various operations on the objects in the list. To provide clear understanding, we will also provide examples and outputs to illustrate the concepts discussed. So, let’s dive into the world of creating lists of objects in Python classes!

Create a class in Python

In short, a class in Python is a blueprint or template for creating objects and defining properties (properties) and behaviors (methods). We use the class keyword, followed by the class name, and define properties and methods in the class block.

This is an example of creating a class in Python:

class Student:
    def __init__(self, name, age, grade):
        self.name = name
        self.age = age
        self.grade = grade

In the above example, we outline a Python class named "Student", which contains a special constructor called "init". Constructors are automatically called when an instance of a class is created by using a class call followed by parentheses. The "init" method accepts three parameters - "name", "age" and "grade" - which are used to initialize the properties of the instance using the "self" keyword.

Create an object of class

In Python, creating an object of a class involves instantiating or creating an instance of the class. Classes serve as blueprints or templates for objects with specific properties and behaviors. After you define a class, you can create multiple objects or instances of that class, each with its own unique set of property values.

Example

This is an example of creating an object or instance of a class:

# Create objects of the Student class
student1 = Student("Alice", 18, "A")
student2 = Student("Bob", 17, "B")
student3 = Student("Charlie", 19, "A+")

# Access and print attributes of the objects
print("Student 1:")
print("Name:", student1.name)
print("Age:", student1.age)
print("Grade:", student1.grade)

print("Student 2:")
print("Name:", student2.name)
print("Age:", student2.age)
print("Grade:", student2.grade)

print("Student 3:")
print("Name:", student3.name)
print("Age:", student3.age)
print("Grade:", student3.grade)

Output

Student 1:
Name: Alice
Age: 18
Grade: A
Student 2:
Name: Bob
Age: 17
Grade: B
Student 3:
Name: Charlie
Age: 19
Grade: A+

In this example, we instantiate three objects of the "Student" class - student1, student2 and student3 - each object has a unique attribute value, including name, age and grades. We then use dot notation to access and print each object's property values. This illustrates the process of creating objects of a class and retrieving their property values ​​to obtain the desired output.

Create a list of objects in a class

In Python, creating a list of objects within a class is a useful feature that allows you to store and manage multiple instances or values ​​of a class. This can be helpful when dealing with objects that have similar characteristics or belong to the same category. Let us explore how to create a list of objects in a class through an example to understand the concept better.

class Student:
    def __init__(self, name, age, grade):
        self.name = name
        self.age = age
        self.grade = grade
        self.students_list = []  # Initialize an empty list to store student objects

    def add_student(self, student):
        self.students_list.append(student)  # Append student objects to the list

# Create student objects
student1 = Student("Alice", 18, "A")
student2 = Student("Bob", 17, "B")
student3 = Student("Charlie", 19, "A+")

# Add student objects to the list
student1.add_student(student1)
student1.add_student(student2)
student1.add_student(student3)

# Access objects in the list
print(student1.students_list) 

Output

[<__main__.Student object at 0x7f8c87e35e80>, <__main__.Student object at 0x7f8c87e35ef0>, <__main__.Student object at 0x7f8c87e35f60>]

The output is appending the list of student objects to the 'students_list' attribute of the 'student1' object. Each object is represented as , where 'xx' is a hexadecimal number representing the memory address of the object. Note that memory addresses may change each time the code is executed because they depend on the system's memory allocation.

Access objects in the list

After adding student objects to "students_list" we can easily access them using standard list indexing or iteration. Let's look at an example to see how to access objects in a list.

class Student:
    def __init__(self, name, age, grade):
        self.name = name
        self.age = age
        self.grade = grade
        self.students_list = []

    def add_student(self, student):
        self.students_list.append(student)

    def get_students(self):
        return self.students_list

# Create student objects
student1 = Student("Alice", 18, "A")
student2 = Student("Bob", 17, "B")
student3 = Student("Charlie", 19, "A+")

# Add student objects to the list
student1.add_student(student1)
student1.add_student(student2)
student1.add_student(student3)

# Access objects in the list
students_list = student1.get_students()  # Get the list of student objects
# Access objects using list indexing
print(students_list[0].name)  
print(students_list[1].name)
print(students_list[2].name) 

Output

Alice
Bob
Charlie

In the output, you can see that all students' names are printed by using the list index number. The "name" property of each student object is then accessed using dot notation, allowing us to get the student's name.

in conclusion

To summarize, leveraging object lists in Python classes is a valuable technique to efficiently store and manage multiple instances of a class. It simplifies the storage, retrieval, and manipulation of objects, thereby simplifying the process of performing various operations on them. You can easily access, add, remove, and modify objects in a list by adding a list property to your class and using class or instance methods to add objects to the list. This approach is particularly advantageous in scenarios where you need to manage multiple instances of a class with similar properties or behavior.

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