Iterating over strings in Python

Introduction

Iterating over strings lets you look at each letter one by one. This helps when you want to check or change parts of a word or sentence.

Counting how many times a letter appears in a word.

Changing all letters in a sentence to uppercase or lowercase.

Finding if a certain letter or symbol is inside a word.

Printing each letter of a word on a new line.

Syntax

Python

for letter in string:
    # do something with letter

The word 'string' is the name of your text variable.

Each 'letter' is one character from the string, one at a time.

Examples

Prints each letter of the word 'hello' on its own line.

Python

word = "hello"
for letter in word:
    print(letter)

Prints each letter in uppercase.

Python

text = "Python"
for char in text:
    print(char.upper())

Counts how many times the letter 'a' appears, ignoring case.

Python

name = "Anna"
count_a = 0
for ch in name:
    if ch == 'a' or ch == 'A':
        count_a += 1
print(count_a)

Sample Program

This program prints each letter in the sentence except spaces.

Python

sentence = "Hello World"
for letter in sentence:
    if letter != ' ':
        print(letter)

Important Notes

Strings are like a list of letters, so you can use a loop to go through them.

Spaces and punctuation are also characters and will be included unless you skip them.

You cannot change letters directly in a string because strings are fixed, but you can build a new string.

Summary

Use a for loop to look at each letter in a string one by one.

You can check, count, or print letters inside the loop.

Remember that strings cannot be changed directly, but you can create new strings from letters.