Looping Statements (Iteration)

Python tutorial · PySpark.in

Looping Statements (Iteration)

Loops are used to execute a block of code repeatedly until a certain condition is met.This process is called iteration.Instead of writing the same line of code multiple times, we can use loops to perform repetitive tasks efficiently.

Types of Loops in Python

Python provides two main types of loops:

for loop
while loop

Additionally, we use nested loops and loop control statements like break, continue, and pass to control loop behavior.

for Loop

The for loop is used to iterate over a sequence such as a list, tuple, dictionary, string, or range of numbers.

Example1 : Looping through a List

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
 print(fruit)

▶ Output will appear here.

Example 2: Using range()

A function that generates a sequence of numbers for controlled iterations.

1for i in range(1, 6):

2 print(i)

▶ Output will appear here.

Example 3: Using for with String

A for loop that iterates through each character in a string.

1for letter in "Python":

2 print(letter)

▶ Output will appear here.

while Loop

The while loop runs as long as a condition is True.When the condition becomes False, the loop stops.

Example 1: Basic while Loop

count = 1
while count <= 5:
 print(count)
 count += 1

▶ Output will appear here.

Example 2: Infinite Loop (Use with Care!)

while True:
 print("This will run forever!")
 break  # stop the loop using break

▶ Output will appear here.

Nested Loops

You can use one loop inside another.These are called nested loops and are often used for working with 2D data (like matrices).

Example:

for i in range(1, 4):
 for j in range(1, 4):
 print(f"i={i}, j={j}")

▶ Output will appear here.

Loop Control Statements

Python provides special statements to control how loops behave.

Statement	Description	Example Meaning
break	Terminates the loop immediately	Stop the loop when i==3
continue	Skips the current iteration and moves to the next	Skip printing when i==3
pass	Does nothing; used as a placeholder	Used for creating empty loops or blocks

Example:

for i in range(1, 6):
 if i == 3:
 continue
 print(i)

▶ Output will appear here.

Using Else with Loops

Python allows an else block with both for and while loops.
The else part is executed only when the loop completes normally (i.e., no break occurs).

Example:

for i in range(1, 4):
 print(i)
else:
 print("Loop completed successfully!")

▶ Output will appear here.

Note: Don’t get confuse

Use for loops when you know how many times to iterate.
Use while loops when the number of iterations is unknown.
Use break, continue, and pass to control loop execution.
Nested loops are useful for multi-dimensional data.
else with loops provides clean post-loop handling.

Looping Statements (Iteration)