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python class attributes vs instance attributes

Helpful Hare answered on June 18, 2023 Popularity 6/10 Helpfulness 8/10

answer python class attributes vs instance attributes

python class attributes vs instance attributes

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In Python, class attributes and instance attributes are two types of attributes that can be defined within a class. Here are the key differences between them:

1 - Definition:

  - Class attributes: These are defined within the class body, outside of any methods. They are shared by all instances of the class.
  - Instance attributes: These are defined within the methods or the __init__ method of a class. They are unique to each instance of the class.

2 - Scope:

  - Class attributes: They have a class-level scope and can be accessed directly using the class name or through any instance of the class.
  - Instance attributes: They have an instance-level scope and are accessed through the specific instance of the class.

3 - Access:

  - Class attributes: They can be accessed and modified by all instances of the class. When an instance tries to access a class attribute, if it doesn't have its own instance attribute with the same name, it falls back to the class attribute.
  - Instance attributes: Each instance has its own copy of instance attributes, and they can be accessed and modified only within that specific instance.

4 - Initialization:

  - Class attributes: They are typically defined directly within the class and do not require any initialization. They are accessible as soon as the class is defined.
  - Instance attributes: They are usually initialized within the __init__ method of the class. Each instance can have different values for the same instance attribute.

5 - Memory allocation:

  - Class attributes: They are allocated memory once, and all instances of the class share the same memory space for class attributes.
  - Instance attributes: Each instance has its own memory space for instance attributes.

Here's an example to illustrate the differences:

class MyClass:
    class_attr = 0  # Class attribute

    def __init__(self, instance_attr):
        self.instance_attr = instance_attr  # Instance attribute

# Accessing class attributes
print(MyClass.class_attr)  # Output: 0

obj1 = MyClass(10)
obj2 = MyClass(20)

# Accessing instance attributes
print(obj1.instance_attr)  # Output: 10
print(obj2.instance_attr)  # Output: 20

# Modifying class attributes
MyClass.class_attr = 5
print(obj1.class_attr)  # Output: 5
print(obj2.class_attr)  # Output: 5

# Modifying instance attributes
obj1.instance_attr = 15
print(obj1.instance_attr)  # Output: 15
print(obj2.instance_attr)  # Output: 20

In the example, class_attr is a class attribute shared by all instances, while instance_attr is an instance attribute specific to each instance.

Popularity 6/10 Helpfulness 8/10 Language python

Source: Grepper

Tags: attributes instance python

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Contributed on Jun 18 2023

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python class attributes vs instance attributes

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