Nested loops are an essential concept in Python programming, where one loop is placed inside another. They allow efficient iteration over multi-dimensional data structures, printing patterns, and handling tabular data. In this guide, we will explore the syntax, use cases, examples, and control statements associated with nested loops.
Nested loops help in:
A nested loop consists of an outer loop and one or more inner loops. The inner loop executes completely for each iteration of the outer loop.
Include a flowchart diagram demonstrating how the outer loop controls the execution of the inner loop.
for
LoopA for
loop inside another for
loop is commonly used when the number of iterations is predefined.
for variable1 in sequence:
for variable2 in sequence:
statement(s)
for i in range(1, 4):
print(f"Multiplication table for {i}:")
for j in range(1, 11):
print(f"{i} x {j} = {i * j}")
print()
Output:
Multiplication table for 1:
1 x 1 = 1
1 x 2 = 2
...
Multiplication table for 2:
2 x 1 = 2
2 x 2 = 4
...
while
LoopA while
loop inside another while
loop is used when the number of iterations is unknown beforehand.
while condition1:
while condition2:
statement(s)
a = 1
while a <= 3:
b = 1
while b <= 3:
print(b, end=' ')
b += 1
print()
a += 1
Output:
1 2 3
1 2 3
1 2 3
for
Inside while
A for
loop can be placed inside a while
loop for repeated execution.
list1 = [40, "Python"]
a = len(list1)
i = 0
while i < a:
for j in list1:
print(j)
i += 1
Output:
40
Python
40
Python
while
Inside for
A while
loop can also be placed inside a for
loop.
list1 = [40, "Python"]
a = len(list1)
for i in list1:
index = 0
while index < a:
print(list1[index])
index += 1
Output:
40
Python
40
Python
break
The break
statement exits the current loop. In nested loops, it only terminates the loop where it is placed.
list1 = [40, "Python", 0, 30.45]
for i in list1:
if i == 0:
break
print(i)
Output:
40
Python
continue
The continue
statement skips the remaining code for the current iteration and moves to the next loop iteration.
list1 = [40, "Python", 0, 30.45]
for i in list1:
if i == 0:
continue
print(i)
Output:
40
Python
30.45
1. What is a nested loop in Python? A nested loop is a loop inside another loop, commonly used to handle multi-dimensional data.
2. How do you break out of nested loops? Use the break
statement to exit the innermost loop. To break out of multiple loops, use flags or exception handling.
3. Can you mix for
and while
loops? Yes, a for
loop can be inside a while
loop, and vice versa.
Mastering nested loops in Python is crucial for efficient programming. Understanding their syntax, use cases, and control statements like break
and continue
will help you solve complex programming challenges. Keep practicing and experimenting to gain deeper insights!