Creating Instance Objects in Python

To create instances of a class, you call the class using class name and pass in whatever arguments its __init__ method accepts.

Creating Instance Objects

When you create an object, Python calls the class constructor (__init__ method) to initialize the new instance ?

# This would create first object of Employee class
emp1 = Employee("Zara", 2000)
# This would create second object of Employee class
emp2 = Employee("Manni", 5000)

Accessing Object Attributes

You access the object's attributes using the dot (.) operator with object. Class variables can be accessed using class name ?

emp1.displayEmployee()
emp2.displayEmployee()
print("Total Employee %d" % Employee.empCount)

Complete Example

Now, putting all the concepts together ?

class Employee:
    'Common base class for all employees'
    empCount = 0
    
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary
        Employee.empCount += 1
    
    def displayCount(self):
        print("Total Employee %d" % Employee.empCount)
    
    def displayEmployee(self):
        print("Name :", self.name, ", Salary:", self.salary)

# This would create first object of Employee class
emp1 = Employee("Zara", 2000)
# This would create second object of Employee class
emp2 = Employee("Manni", 5000)

emp1.displayEmployee()
emp2.displayEmployee()
print("Total Employee %d" % Employee.empCount)

Name : Zara , Salary: 2000
Name : Manni , Salary: 5000
Total Employee 2

Modifying Object Attributes

You can add, remove, or modify attributes of classes and objects at any time ?

emp1.age = 7  # Add an 'age' attribute
emp1.age = 8  # Modify 'age' attribute
del emp1.age  # Delete 'age' attribute

Built-in Attribute Functions

Instead of using the normal statements to access attributes, you can use the following functions ?

• The getattr(obj, name[, default]) ? to access the attribute of object.
• The hasattr(obj,name) ? to check if an attribute exists or not.
• The setattr(obj,name,value) ? to set an attribute. If attribute does not exist, then it would be created.
• The delattr(obj, name) ? to delete an attribute.

class Employee:
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

emp1 = Employee("John", 3000)

print(hasattr(emp1, 'age'))    # Returns True if 'age' attribute exists
setattr(emp1, 'age', 25)       # Set attribute 'age' to 25
print(getattr(emp1, 'age'))    # Returns value of 'age' attribute
delattr(emp1, 'age')           # Delete attribute 'age'

False
25

Conclusion

Creating instance objects in Python involves calling the class constructor with required arguments. You can access and modify attributes using dot notation or built-in functions like getattr() and setattr().