Python For Loop

For Loop → mainly used for sequential traversal (going through elements one by one)

string = "hello"
 
# in → membership operator (checks presence / iterates)
for var in string:
    print(var)

output

h
e
l
l
o

Syntax

#                  ┌────────── sequence (string, list, range)
#                  │
for variable in sequence:
    print(variable)

If you want to check whether something exists in a sequence:

string = "hello"
 
if 'o' in string:
    print("o exists in the string")
 
if 'x' in string:
    print("x exists in the string")

output

o exists in the string

Sequence = ordered collection
Examples: string, list, range

• range()

Used to generate numbers

#          ┌──────── max value (not included)
#          │
for i in range(5):
    print(i)

output

0
1
2
3
4

for i in range(5):
    print(i + 1)

output

1
2
3
4
5

Note

range(5) → starts from 0 and ends at 4 (5 not included)

• count characters

word = "artificial Intelligence"
count = 0
 
for ch in word:
    if ch == 'i':
        count += 1
 
print("count of i =", count)

output

count of i = 3

Note

• for loop works with sequences
• in is used for iteration and checking
• Always use : and proper indentation Here’s your note cleaned, fixed, and expanded (keeping your style but making it clearer and more complete):

Question

Write a program in Python to count vowels in a given string

word = "artificial"
count = 0
 
for ch in word:
    if ch == 'a' or ch == 'e' or ch == 'i' or ch == 'o' or ch == 'u':
        count += 1
 
print("Total vowels =", count)

output

Total vowels = 5

Note

• Vowels → a, e, i, o, u
• Loop checks each character one by one