Instance attributes in Python - Step-by-Step Execution

Concept Flow - Instance attributes

Create object from class

↓

Call __init__ method

↓

Set instance attributes

↓

Object ready with own data

↓

Access or modify attributes

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Use attributes in methods or outside

When you create an object, Python runs __init__ to set up instance attributes that hold data unique to that object.

Execution Sample

Python

class Dog:
    def __init__(self, name):
        self.name = name

d = Dog('Buddy')
print(d.name)

This code creates a Dog object with a name attribute and prints it.

Execution Table

Step	Action	Evaluation	Result
1	Create Dog object d with name 'Buddy'	Calls Dog.__init__(d, 'Buddy')	d.name set to 'Buddy'
2	Access d.name	Look up attribute 'name' on d	'Buddy'
3	Print d.name	Output the string stored in d.name	Buddy

💡 Program ends after printing the instance attribute value

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
d	undefined	Dog object with name='Buddy'	Dog object with name='Buddy'	Dog object with name='Buddy'
d.name	undefined	'Buddy'	'Buddy'	'Buddy'

Key Moments - 2 Insights

Why do we use self.name = name inside __init__?

self.name = name sets the instance attribute 'name' for that specific object. See execution_table step 1 where d.name is set to 'Buddy'. Without self, the name would be just a local variable.

Can different objects have different values for the same attribute?

Yes! Each object has its own instance attributes. If you create another Dog with a different name, it will have its own separate name. This is shown by how d.name holds 'Buddy' only for that object.

Visual Quiz - 3 Questions

Look at the execution_table step 1, what does self.name get set to?

A The class Dog

B 'self'

C 'Buddy'

D Undefined

💡 Hint

Check the 'Result' column in step 1 where d.name is set to 'Buddy'

At which step is the instance attribute 'name' accessed to print?

A Step 2

B Step 3

C Step 1

D None

💡 Hint

Look at the 'Action' column in step 3 where d.name is printed

If we create another Dog object with name 'Max', what will d.name be?

A 'Buddy'

B 'Max'

C Undefined

D Error

💡 Hint

Instance attributes belong to each object separately as shown in variable_tracker for d.name

Concept Snapshot

Instance attributes are variables tied to an object.
They are set inside __init__ using self.attribute = value.
Each object has its own copy of these attributes.
Access them with object.attribute syntax.
They store data unique to each object.

Full Transcript

When you create an object from a class in Python, the __init__ method runs automatically. Inside __init__, you use self.attribute = value to create instance attributes. These attributes belong to that specific object only. For example, when we create a Dog object with name 'Buddy', the attribute name is set to 'Buddy' for that object. You can access this attribute later using object.attribute, like d.name. Different objects can have different values for the same attribute name. This lets each object keep its own data separate.