Loops and Iteration


🔁 Loops and Iteration

Description: Loops allow you to repeat code without writing it many times. This is useful for handling lists, strings, or running logic multiple times.


Basic for loop

for i in range(5):
    print(i)
0
1
2
3
4



Basic while loop

i = 0
while i < 5:
    print(i)
    i += 1
0
1
2
3
4



Loop through a list

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



Loop through a string

word = "loop"
for char in word:
    print(char)
l
o
o
p



Using break

for i in range(10):
    if i == 5:
        break
    print(i)
0
1
2
3
4



Using continue

for i in range(5):
    if i == 2:
        continue
    print(i)
0
1
3
4



Using pass

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



Using range(start, stop, step)

for i in range(1, 10, 2):
    print(i)
1
3
5
7
9



Nested for loops

for i in range(2):
    for j in range(2):
        print(i, j)
0 0
0 1
1 0
1 1



While loop with countdown

count = 3
while count > 0:
    print("Countdown:", count)
    count -= 1
Countdown: 3
Countdown: 2
Countdown: 1



Sum using loop

total = 0
for i in range(1, 6):
    total += i
print("Sum:", total)
Sum: 15



Find even numbers

for i in range(1, 6):
    if i % 2 == 0:
        print(i, "is even")
2 is even
4 is even



✅ Summary

  • for loops are for sequences (like lists, strings, or ranges).
  • while loops run while a condition is true.
  • break exits the loop early.
  • continue skips the current iteration.
  • pass does nothing (placeholder).