📘 Nested while Loop in Python

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🎯 What is Nested while Loop?

A nested while loop means a while loop inside another while loop.

It is used when:

• patterns
• tables
• grids
• matrix operations
• repeated iterations inside iterations

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📌 Definition

A nested while loop is a loop structure where one while loop is placed inside another while loop.

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🧠 Syntax

while condition1:
    while condition2:
        # code

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🔁 Key Concept

• Outer loop = rows
• Inner loop = columns
• Inner loop completes fully for each outer loop

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📘 Pattern Programs (Code + Output)

1. Square Pattern

CODE:
i = 1
while i <= 5:
    j = 1
    while j <= 5:
        print("*", end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
* * * * *
* * * * *
* * * * *
* * * * *
* * * * *

2. Right Triangle

CODE:
i = 1
while i <= 5:
    j = 1
    while j <= i:
        print("*", end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
*
* *
* * *
* * * *
* * * * *

3. Reverse Triangle

CODE:
i = 5
while i >= 1:
    j = 1
    while j <= i:
        print("*", end=" ")
        j += 1
    print()
    i -= 1

OUTPUT:
* * * * *
* * * *
* * *
* *
*

4. Number Triangle

CODE:
i = 1
while i <= 5:
    j = 1
    while j <= i:
        print(j, end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

5. Same Number Pattern

CODE:
i = 1
while i <= 5:
    j = 1
    while j <= i:
        print(i, end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
1
2 2
3 3 3
4 4 4 4
5 5 5 5 5

6. Floyd’s Triangle

CODE:
num = 1
i = 1
while i <= 5:
    j = 1
    while j <= i:
        print(num, end=" ")
        num += 1
        j += 1
    print()
    i += 1

OUTPUT:
1
2 3
4 5 6
7 8 9 10
11 12 13 14 15

7. Pyramid Pattern (IMPORTANT)

CODE:
i = 1
while i <= 5:
    print(" "*(5-i), end="")
    j = 1
    while j <= i:
        print("*", end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
    *
   * *
  * * *
 * * * *
* * * * *

8. Number Pyramid

CODE:
i = 1
while i <= 5:
    print(" "*(5-i), end="")
    j = 1
    while j <= i:
        print(j, end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
    1
   1 2
  1 2 3
 1 2 3 4
1 2 3 4 5

9. Reverse Number Pattern

CODE:
i = 5
while i >= 1:
    j = 1
    while j <= i:
        print(j, end=" ")
        j += 1
    print()
    i -= 1

OUTPUT:
5 4 3 2 1
4 3 2 1
3 2 1
2 1
1

10. Alphabet Pattern

CODE:
i = 0
while i < 5:
    j = 0
    while j <= i:
        print(chr(65+j), end=" ")
        j += 1
    print()
    i += 1

OUTPUT:
A
A B
A B C
A B C D
A B C D E