Getter and setter methods in Python - Step-by-Step Execution

Concept Flow - Getter and setter methods

Create object with private attribute

↓

Call getter method

↓

Return attribute value

↓

Call setter method

↓

Update attribute value

↓

Call getter method again

↓

Return updated value

This flow shows how an object with private data uses getter to read and setter to update the value safely.

Execution Sample

Python

class Person:
    def __init__(self, name):
        self._name = name
    def get_name(self):
        return self._name
    def set_name(self, new_name):
        self._name = new_name

p = Person('Alice')
print(p.get_name())
p.set_name('Bob')
print(p.get_name())

This code creates a Person with a private name, reads it, changes it, then reads the new name.

Execution Table

Step	Action	Variable/Method	Value/Result	Output
1	Create Person object	p._name	'Alice'
2	Call get_name()	p.get_name()	'Alice'	Alice
3	Call set_name('Bob')	p._name	'Bob'
4	Call get_name() again	p.get_name()	'Bob'	Bob
5	End of program			Execution stops

💡 Program ends after printing updated name 'Bob'

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
p._name	undefined	'Alice'	'Bob'	'Bob'

Key Moments - 3 Insights

Why do we use get_name() instead of accessing p._name directly?

Using get_name() allows controlled access to the private variable _name, as shown in step 2 of the execution_table, which helps protect the data.

What happens if we call set_name() with a new value?

As seen in step 3, set_name() updates the private variable _name safely, changing it from 'Alice' to 'Bob'.

Why is the variable named _name with an underscore?

The underscore signals that _name is meant to be private and should not be accessed directly, encouraging use of getter and setter methods.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of p._name after step 3?

A 'Bob'

B 'Alice'

C undefined

D None

💡 Hint

Check the 'Variable/Method' and 'Value/Result' columns at step 3 in the execution_table.

At which step does the program print 'Alice'?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Output' column in the execution_table for when 'Alice' is printed.

If we remove the set_name method call, what will be printed at step 4?

A 'Bob'

B 'Alice'

C Error

D None

💡 Hint

Refer to variable_tracker to see if p._name changes without set_name call.

Concept Snapshot

Getter and setter methods control access to private data.
Use get_name() to read and set_name() to update.
Private variables use underscore prefix (_name).
This protects data and allows validation.
Call getters and setters instead of direct access.

Full Transcript

This lesson shows how getter and setter methods work in Python. We create a class Person with a private variable _name. The get_name method returns the current name, and set_name updates it. We trace the program creating a Person named Alice, printing the name, changing it to Bob, and printing again. The execution table shows each step and variable changes. Key moments explain why we use getters and setters and the meaning of the underscore. The quiz asks about variable values and outputs at different steps. The snapshot summarizes how getters and setters protect and manage private data.