NESTED LOOP

M3-R5.1 · Chapter 4: Operators, Expressions and Python Statements · 3 min read

Nested Loop in Python

A loop inside another loop is known as nested loop. In nested loop , the inner loop must terminate before the ending of the outer loop
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A nested loop in Python refers to a loop inside another loop. This structure allows you to iterate over multi-dimensional data, such as lists of lists or matrices. Each iteration of the outer loop triggers a complete cycle of the inner loop

Nested while Loop : The while loop having one or more inner while loops are nested while loop.

Syntax:

while expression:

statement(s)

Example 1:

i = 1

while i <=10:

j = 1

while j <=10:

print(i*j,end="\t")

j = j + 1

print("")

i = i + 1

print("Complete!")

Example 2:

i = 1

while i <= 3: # Outer loop

j = 1

while j <= 2: # Inner loop

print(f"Outer loop {i}, Inner loop {j}")

j += 1

i += 1

In this example, the outer loop runs three times (i from 1 to 3), and inside each iteration, the inner loop runs twice (j from 1 to 2). So overall, the inner loop executes 3 × 2 = 6 times.

rows = 5

i = 1

while i <= rows: # Outer loop

j = 1

while j <= i: # Inner loop

print("*", end=" ")

j += 1

print() # Move to the next line

i += 1

* *

* * *

* * * *

* * * * *

The outer loop (i) controls the number of rows.

The inner loop (j) controls how many stars (*) are printed per row.

The end=" " ensures the stars stay on the same line, while print() moves to the next row

x=10

while x>1:

y=10

while y>=x:

print(x, end="")

y-=1

x-=1

print("")

Nested for Loop: The for loop having one or more inner for loops is nested for loop.

Basic Syntax:

for var in sequence:

for var1 in sequence:

statements(s)

for i in range(a):

for j in range(b):

statement of j loop

statement of i loop

Example: