Python Loops

The following loops are available in Python to fulfil the looping needs. Python offers 3 choices for running the loops. The basic functionality of all the techniques is the same, although the syntax and the amount of time required for checking the condition differ.

We can run a single statement or set of statements repeatedly using a loop command.

There are two primary types of loops in Python:

1. for loop
2. while loop

1. for Loop

In Python, the for loop iterates over a sequence: like a list or tuple or string or range. It executes a block of code for each item in the sequence.

Syntax:

for variable in sequence:
    # Code block to execute

Examples:

1. Iterating over a list:

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

Output:

apple
banana
cherry

2. Using range:

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

Output:

0
1
2
3
4

3. Iterating over a string:

for char in "hello":
    print(char)

Output:

h
e
l
l
o

4. With else: The else block runs after the for loop finishes unless the loop is terminated with a break.

for i in range(3):
    print(i)
else:
    print("Loop finished")

Output:

0
1
2
Loop finished

2. while loop

It performs as long as a given condition is True. It is applied when the number of iterations is not known beforehand.

Syntax:

while condition:
    # Code block to execute

Examples:

1. Basic Example

count = 0
while count < 5:
   print(count)
   count += 1

Output:

0
1
2
3
4

2. With break: The break statement immediately exits the loop.

count = 0
while True:
   print(count)
   count += 1
   if count == 3:
     break

Output:

0
1
2

3. With else: Like the for loop, the else block executes unless the loop is terminated with a break.

count = 0
while count < 3:
  print(count)
  count += 1
else:
  print("Finished")

Output:

0
1
2
Finished

Special Control Statements

1. break: Exits the loop entirely.

for i in range(5):
    if i == 3:
       break
    print(i)

Output:

0
1
2

2. continue: skips the current iteration and continues to the next one.

for i in range(5):
    if i == 3:
      continue
    print(i)

Output:

0
1
2
4

3. pass: Does nothing; used as a placeholder.

for i in range(5):
    if i == 3:
       pass
    print(i)

Output:

0
1
2
3
4

Key Points to Remember

• The for loop is typically used when you know the number of iterations or are iterating over a sequence.
• A while loop is used when the number of iterations depends on some condition.
• Use break to exit the loop early and continue to skip an iteration.
• Use else for clean-up or further steps when a loop naturally ends.