Artificial Intelligence for Beginners Course for Roppongi Kids

1. Introduction: Iterating Over Data Structures

In Python, loops are not limited to repeating numbers or executing counters; they are frequently used to iterate across data structures such as strings and lists.

Because a text string is an ordered sequence of individual characters, a loop can step through each character one by one. By looping through strings, you can inspect individual letters, search for specific patterns, count character occurrences, and manipulate text data programmatically.

2. Example 1: Character-by-Character Iteration

for char in "Python":
    print(char)

How It Works & Output

P
y
t
h
o
n

3. Example 2: Counting Specific Character Occurrences

count = 0
for char in "banana":
    if char == "a":
        count += 1
print("Total occurrences of 'a':", count)

Execution Result: Total occurrences of 'a': 3

4. Example 3: Reversing a String Using a Loop

text = "Python"
reversed_text = ""
for char in text:
    reversed_text = char + reversed_text
print("Reversed string:", reversed_text)

Output: Reversed string: nohtyP

5. Summary

• Strings are iterable sequences of characters.
• Combine for with if to count or filter characters.
• Prepending characters can reverse a string.