Python Nested Loops

1. Basic Nested For Loop Syntax

A simple demonstration showing how the inner loop cycles completely through its range for each outer loop count.

Python

for i in range(1, 3):       # Outer loop
    for j in range(1, 4):   # Inner loop
        print(f"Outer: {i}, Inner: {j}")

Output: Outer: 1, Inner: 1 Outer: 1, Inner: 2 Outer: 1, Inner: 3 Outer: 2, Inner: 1 Outer: 2, Inner: 2 Outer: 2, Inner: 3

Real-Time Example 1: Movie Theater Seating Grid Mapping

Generate and label all seat numbers in a cinema hall layout organized by rows and seat numbers.

Python

rows = ['A', 'B', 'C']
seat_numbers = range(1, 4)

print("Theater Seating Layout:")
for row in rows:
    for seat in seat_numbers:
        print(f"Seat Tag: {row}{seat}")

Output: Theater Seating Layout: Seat Tag: A1 Seat Tag: A2 Seat Tag: A3 Seat Tag: B1 Seat Tag: B2 Seat Tag: B3 Seat Tag: C1 Seat Tag: C2 Seat Tag: C3

Real-Time Example 2: Multiplication Matrix Generator (Billing/Pricing)

Generate a multiplication lookup table used for bulk pricing computations.

Python

print("Multiplication Table Grid (1 to 3):")
for i in range(1, 4):
    for j in range(1, 4):
        print(f"{i} x {j} = {i * j}", end="\t")
    print() # New line after inner loop completes

Output: Multiplication Table Grid (1 to 3): 1 x 1 = 1 1 x 2 = 2 1 x 3 = 3 2 x 1 = 2 2 x 2 = 4 2 x 3 = 6 3 x 1 = 3 3 x 2 = 6 3 x 3 = 9

Real-Time Example 3: Warehouse Inventory Bin Location Mapping

Traverse stock room rack zones and shelf tiers to audit inventory location tags.

Python

zones = ["Zone-North", "Zone-South"]
shelfs = ["Shelf-1", "Shelf-2"]

for zone in zones:
    for shelf in shelfs:
        print(f"Scanning storage location -> {zone} : {shelf}")

Output: Scanning storage location -> Zone-North : Shelf-1 Scanning storage location -> Zone-North : Shelf-2 Scanning storage location -> Zone-South : Shelf-1 Scanning storage location -> Zone-South : Shelf-2

Real-Time Example 4: Restaurant Menu Combination Builder

Generate all possible combo meal options pairing main courses with beverages.

Python

mains = ["Burger", "Pizza"]
drinks = ["Cola", "Lemonade", "Iced Tea"]

print("Available Meal Combos:")
for main in mains:
    for drink in drinks:
        print(f"Combo: {main} + {drink}")

Output: Available Meal Combos: Combo: Burger + Cola Combo: Burger + Lemonade Combo: Burger + Iced Tea Combo: Pizza + Cola Combo: Pizza + Lemonade Combo: Pizza + Iced Tea

Real-Time Example 5: 2D Matrix Grid Summation (Sales Analytics)

Calculate total annual revenue by summing up values inside a 2D quarterly sales matrix.

Python

# Quarterly branch sales data (Branch 1, Branch 2)
sales_matrix = [
    [12000, 15000, 13000],
    [18000, 16000, 19000]
]
total_revenue = 0

for branch in sales_matrix:
    for quarter_sales in branch:
        total_revenue += quarter_sales

print("Total Corporate Revenue across all branches: ₹", total_revenue)

Output: Total Corporate Revenue across all branches: ₹ 93000

Real-Time Example 6: School Exam Schedule Slotting

Pair exam subjects with available morning and evening time slots.

Python

subjects = ["Maths", "Science"]
time_slots = ["Morning Shift", "Evening Shift"]

print("Exam Schedule Allocations:")
for sub in subjects:
    for slot in time_slots:
        print(f"Exam: {sub} scheduled in {slot}")

Output: Exam Schedule Allocations: Exam: Maths scheduled in Morning Shift Exam: Maths scheduled in Evening Shift Exam: Science scheduled in Morning Shift Exam: Science scheduled in Evening Shift

Real-Time Example 7: Pattern Printing (Star Triangle UI Design)

Use nested loops to construct geometric patterns for console UI decoration.

Python

print("Star Pyramid Pattern:")
for i in range(1, 5):
    for j in range(i):
        print("*", end=" ")
    print()

Output: Star Pyramid Pattern: * * * * * * * * * *

Real-Time Example 8: E-Commerce Variant SKU Generator

Generate unique Stock Keeping Unit (SKU) combinations for products available in multiple sizes and colors.

Python

product_name = "T-Shirt"
sizes = ["S", "M", "L"]
colors = ["Red", "Blue"]

print("Generated Product Variants:")
for size in sizes:
    for color in colors:
        print(f"SKU Code: {product_name}-{size}-{color}")

Output: Generated Product Variants: SKU Code: T-Shirt-S-Red SKU Code: T-Shirt-S-Blue SKU Code: T-Shirt-M-Red SKU Code: T-Shirt-M-Blue SKU Code: T-Shirt-L-Red SKU Code: T-Shirt-L-Blue

Real-Time Example 9: Finding Duplicate Items in Two Lists

Compare two distinct inventory lists using nested loops to locate matching catalog items.

Python

store_a_items = ["Laptop", "Mouse", "Keyboard"]
store_b_items = ["Monitor", "Mouse", "Keyboard"]

print("Common Items Found in Both Stores:")
for item_a in store_a_items:
    for item_b in store_b_items:
        if item_a == item_b:
            print(f"- Match: {item_a}")

Output: Common Items Found in Both Stores: - Match: Mouse - Match: Keyboard

Real-Time Example 10: Nested Loop with Break Statement

Break out of the inner loop early when a specific threshold condition is met.

Python

for week in range(1, 3):
    print(f"--- Week {week} ---")
    for day in range(1, 8):
        if day > 3:
            print("  Mid-week rest triggered. Breaking inner day loop.")
            break
        print(f"  Processing Day {day}")

Output: --- Week 1 --- Processing Day 1 Processing Day 2 Processing Day 3 Mid-week rest triggered. Breaking inner day loop. --- Week 2 --- Processing Day 1 Processing Day 2 Processing Day 3 Mid-week rest triggered. Breaking inner day loop.

Summary of Nested Loops

Definition: A loop placed inside the body of another loop.
Execution Rule: The inner loop executes completely for every single iteration of the outer loop.
Applications: Perfect for matrix manipulation, coordinate systems, grid layouts, product variants, and multi-dimensional reports.

🔲 What is a Nested Loop in Python?

Summary of Nested Loops