Procedural vs object-oriented approach in Python - Visual Side-by-Side Comparison

Concept Flow - Procedural vs object-oriented approach

Start

↓

Choose Approach

↓

Procedural

→Write functions

↓

Object-Oriented

→Define class

This flow shows two ways to organize code: procedural uses functions step-by-step, object-oriented uses classes and objects with methods.

Execution Sample

Python

def add_proc(x, y):
    return x + y

class Adder:
    def add(self, x, y):
        return x + y

result_proc = add_proc(2, 3)
adder = Adder()
result_obj = adder.add(2, 3)
print(result_proc)
print(result_obj)

This code shows adding two numbers using a procedural function and an object-oriented class method.

Execution Table

Step	Action	Evaluation	Result
1	Define function add_proc	Store function in memory	Function ready to use
2	Define class Adder with method add	Store class and method	Class ready to create objects
3	Call add_proc(2, 3)	Add 2 + 3	5
4	Create object adder = Adder()	Allocate object	Object adder created
5	Call adder.add(2, 3)	Call method add with 2,3	5
6	Print results	Output values	5 and 5 printed

💡 All steps executed, program ends after printing results

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 5	Final
add_proc	undefined	function stored	function stored	function stored	function stored
Adder	undefined	class stored	class stored	class stored	class stored
adder	undefined	undefined	object created	object created	object created
result_proc	undefined	5	5	5	5
result_obj	undefined	undefined	undefined	5	5

Key Moments - 3 Insights

Why do we need to create an object to use the add method in the object-oriented approach?

Because the add method is inside the class and works on objects, so we must create an object (see execution_table step 4 and 5) to call the method.

Can we call the procedural function without creating anything?

Yes, the procedural function is standalone and can be called directly (see execution_table step 3).

Are the results from both approaches the same?

Yes, both return 5 when adding 2 and 3 (see execution_table steps 3 and 5).

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of calling add_proc(2, 3)?

A 2

B 3

C 5

D Error

💡 Hint

Check execution_table row 3 under Result column

At which step is the object 'adder' created?

A Step 4

B Step 3

C Step 5

D Step 2

💡 Hint

Look at execution_table row 4 Action column

If we remove the class and only keep the procedural function, what changes in variable_tracker?

A 'result_obj' will be 5

B 'adder' variable will be undefined throughout

C 'add_proc' will be undefined

D 'Adder' will be an object

💡 Hint

See variable_tracker row for 'adder' which is created only after Step 4

Concept Snapshot

Procedural approach:
- Write functions
- Call functions directly
- Simple and linear

Object-oriented approach:
- Define classes
- Create objects
- Call methods on objects

Both can produce same results but organize code differently.

Full Transcript

This lesson compares procedural and object-oriented programming. Procedural uses functions you call directly. Object-oriented uses classes to create objects, then calls methods on those objects. The example adds two numbers both ways. The execution table shows defining functions and classes, calling them, and printing results. Variables track function, class, and object states. Key moments clarify why objects are needed for methods and that procedural functions are standalone. The quiz checks understanding of steps and variable states. The snapshot summarizes the main differences simply.

Practice

1. Which statement best describes the main difference between procedural and object-oriented programming in Python?

easy

A. Procedural programming is faster than object-oriented programming in all cases.

B. Procedural programming is only for small programs; object-oriented programming is for large programs.

C. Procedural programming cannot use variables; object-oriented programming can.

D. Procedural programming uses functions and step-by-step instructions; object-oriented programming uses classes and objects.

Solution

1. Step 1: Understand procedural programming basics

   Procedural programming organizes code as functions and instructions executed in order.

2. Step 2: Understand object-oriented programming basics

   Object-oriented programming organizes code using classes and objects that combine data and behavior.

3. Final Answer:

   Procedural programming uses functions and step-by-step instructions; object-oriented programming uses classes and objects. -> Option D

4. Quick Check:

   Procedural = functions, OOP = classes/objects [OK]

Hint: Procedural = steps; OOP = objects/classes [OK]

Common Mistakes:

• Thinking procedural can't use variables
• Believing OOP is always slower
• Confusing program size with programming style

2. Which of the following is the correct way to define a class in Python?

easy

A. def MyClass(): pass

B. class MyClass(): pass

C. function MyClass() {}

D. class MyClass[]: pass

Solution

1. Step 1: Recall Python class syntax

   In Python, classes are defined using the keyword class followed by the class name and parentheses.

2. Step 2: Check each option

   class MyClass(): pass uses correct Python syntax. def MyClass(): pass uses def which defines a function, not a class. function MyClass() {} uses JavaScript syntax. class MyClass[]: pass uses invalid brackets.

3. Final Answer:

   class MyClass(): pass -> Option B

4. Quick Check:

   Python classes start with 'class' keyword [OK]

Hint: Classes start with 'class' keyword in Python [OK]

Common Mistakes:

• Using def instead of class
• Using wrong brackets [] instead of ()
• Confusing Python with other languages syntax

3. What will be the output of this Python code?

def greet(name):
    return f"Hello, {name}!"

class Person:
    def __init__(self, name):
        self.name = name
    def greet(self):
        return greet(self.name)

p = Person("Anna")
print(p.greet())

medium

A. TypeError

B. Hello, name!

C. Hello, Anna!

D. AttributeError

Solution

1. Step 1: Understand the procedural function greet

   The function greet(name) returns the string "Hello, {name}!" with the given name.

2. Step 2: Understand the Person class and method call

   The Person class stores the name and its greet method calls the procedural greet function with self.name. Creating p with name "Anna" and calling p.greet() returns "Hello, Anna!".

3. Final Answer:

   Hello, Anna! -> Option C

4. Quick Check:

   Class method calls procedural function correctly [OK]

Hint: Class method calls function with self.name [OK]

Common Mistakes:

• Confusing variable name with string 'name'
• Expecting error due to mixing styles
• Forgetting to use self.name

4. Identify the error in this code that mixes procedural and object-oriented styles:

class Calculator:
    def add(self, a, b):
        return a + b

result = Calculator.add(3, 4)
print(result)

medium

A. Missing self argument when calling add method

B. Class Calculator is not defined

C. add method should not return a value

D. print statement syntax error

Solution

1. Step 1: Understand method call on class vs instance

   The add method is an instance method requiring a self parameter. Calling Calculator.add(3, 4) misses the self argument.

2. Step 2: Correct usage

   To fix, create an instance: calc = Calculator() then call calc.add(3, 4). This passes self automatically.

3. Final Answer:

   Missing self argument when calling add method -> Option A

4. Quick Check:

   Instance methods need self, call via instance [OK]

Hint: Call instance methods on object, not class [OK]

Common Mistakes:

• Calling instance method directly on class
• Ignoring self parameter
• Assuming methods are static by default

5. You want to convert this procedural code into an object-oriented style. Which class design correctly encapsulates the data and behavior?

# Procedural code
def area_rectangle(width, height):
    return width * height

w = 5
h = 3
print(area_rectangle(w, h))

hard

A. class Rectangle:
def __init__(self, width, height):
self.width = width
self.height = height
def area(self):
return self.width * self.height

B. class Rectangle:
def area(width, height):
return width * height

C. class Rectangle:
def __init__(self):
pass
def area(self):
return width * height

D. class Rectangle:
def __init__(self, width, height):
return width * height

Solution

1. Step 1: Identify data and behavior to encapsulate

   The procedural code uses width and height as data and area_rectangle as behavior. In OOP, these should be inside a class.

2. Step 2: Check class options for correct encapsulation

   class Rectangle: def __init__(self, width, height): self.width = width self.height = height def area(self): return self.width * self.height stores width and height as instance variables and defines area() method using them. Other options either miss self, lack data storage, or misuse return in constructor.

3. Final Answer:

   class Rectangle with __init__ storing width and height, and area method using them -> Option A

4. Quick Check:

   OOP encapsulates data and behavior in class [OK]

Hint: Store data in __init__, use methods for behavior [OK]

Common Mistakes:

• Not using self for instance variables
• Returning values from __init__
• Defining methods without self parameter