Topic 6:- Python blocks?

What are Python Blocks?  

 (Reading time-5 to 7 minutes)

A block in Python is a group of statements that are executed together. Blocks define the structure and scope of your program (what belongs where).

Every block starts with a header line (like if, for, def, or class) and is followed by an indented set of statements.

Common Types of Blocks in Python

1. Conditional Block — using if, elif, else

2. Loop Block — using for, while

3. Function Block — using def

4. Class Block — using class

1. Conditional Block:

A conditional block uses keywords like if, elif, and else to check conditions and control the flow of execution.

Conditional Block

Real-Life example:

Conditional blocks work like traffic signals:

• 🟢 If the light is green → Go

• 🟡 Else if the light is yellow → Slow down

• 🔴 Else → Stop

Syntex- 

if True:
    print("This is an if block")
elif:
    print("This is an elif block")

else:

    print("This is an else block")

Here, the indented part after if, elif or else is a block.

2. Loop Block:

A loop block in Python is a group of statements that executes repeatedly as long as a given condition is True. It helps in repeating tasks without writing the same code multiple times.

Loop Structure flowchart

Syntex:

for i in range(n):

    print("Inside loop:", n)
print("Outside loop")

Types of Loops in Python

for loop → used when you know how many times to repeatSyntex
     Example 
             for i in range(5):
                  print("Iteration:", i)
       
     Output:  Iteration: 0
                Iteration: 1
                Iteration: 2
                Iteration: 3
                Iteration: 4

2. while loop → used when you repeat until a condition becomes false.

Syntex 

          while condition:
                 # loop block
     Example:
             count = 1             while count <= 3:
                    print("Count =", count)
                    count += 1

         Output: 

                            Count = 1

                            Count = 2

                            Count = 3

The indented statement under the for loop belongs to the loop block.The last print is outside the block (no indentation).

Why Use Loop?

Purpose	Explanation
Automation	Repeat tasks automatically
Efficiency	Avoid writing repetitive code
Data Processing	Iterate through lists, files, datasets
Dynamic Logic	Run code until a condition changes

3. Function Block:

A Function Block in Python is a group of related statements that perform a specific task.
Functions make your program modular, organized, and reusable. A function is defined using the keyword def, followed by the function name and parentheses ().

Syntex: 

    def greet():
        print("Hello, world!")
        print("Welcome to Python")

    greet()

All statements inside the function (indented equally) form a function block.

4. Class Block:

Syntex

class Student:
    def display(self):
        print("This is a class block")

obj = Student()
obj.display()

Here, both class Student: and the function inside it are nested blocks.

Important Rule — Indentation

Python uses indentation (spaces or tabs) to define blocks. Unlike other languages (C, Java), Python doesn’t use braces {}.

Example of indentation error:

if True:
print("Error!")   # Incorrect — not indented

This will raise:

IndentationError: expected an indented block

Summary

Concept	Description	Example Keyword
Block	Group of statements executed together	if, for, def, class
Defined by	Indentation (4 spaces recommended)	—
Purpose	Structure & scope of code	—