Python Loops

In Python, loops are used to repeatedly execute a block of code as long as a certain condition is met. Python supports two types of loops: for loops and while loops. Here's an explanation of each type with simple examples.

1. For Loop

The for loop in Python is used to iterate over a sequence (such as a list, tuple, dictionary, set, or string). It executes a block of code once for each item in the sequence.

Example 1: Iterating through a list

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

Example 2: Iterating through a string

for char in "hello":
    print(char)

Output:

h
e
l
l
o

Example 3: Using range()

for i in range(5):
    print(i)

Output:

0
1
2
3
4

2. While Loop

The while loop in Python repeatedly executes a block of code as long as a given condition is true.

Example 4: Basic while loop

count = 0

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

Output:

0
1
2
3
4

Example 5: while loop with a condition

number = 10

while number > 0:
    print(number)
    number -= 2

Output:

10
8
6
4
2

3. Nested Loops

You can also nest loops inside each other.

Example 6: Nested for loop

for i in range(3):
    for j in range(2):
        print(f"i={i}, j={j}")

Output:

i=0, j=0
i=0, j=1
i=1, j=0
i=1, j=1
i=2, j=0
i=2, j=1

4. Control Statements

Python provides several control statements to control the flow of loops:

• break: Exits the loop prematurely.
• continue: Skips the rest of the code inside the loop for the current iteration and moves to the next iteration.
• else: Executes a block of code once when the loop is finished (only if the loop is not terminated by a break statement).

Example 7: Using break

for i in range(10):
    if i == 5:
        break
    print(i)

Output:

0
1
2
3
4

Example 8: Using continue

for i in range(10):
    if i % 2 == 0:
        continue
    print(i)

Output:

1
3
5
7
9

Example 9: Using else with loops

for i in range(5):
    print(i)
else:
    print("Loop finished")

Output:

0
1
2
3
4
Loop finished

Summary

• for loop: Used to iterate over a sequence.
• while loop: Repeatedly executes a block of code as long as a condition is true.
• Nested loops: Loops inside loops for more complex iterations.
• Control statements: break, continue, and else to control the flow of loops.