String manipulation without in built methods in Python Part 3

In today's post, we dive into more exercises focused on string manipulation without using any built-in methods in Python.

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Problem One: Swap Adjacent Characters

Task:

You are given a string s. Your task is to write a function that returns a string in which every pair of adjacent characters in the original string is swapped.

If the string has an odd length, leave the last character as it is.

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Explanation

Imagine you're given "abcdef" — the goal is to swap every adjacent character:

• Swap a and b, then c and d, then e and f → Result: "badcfe"

Now if the string has an odd length, like "hello", you’d swap h and e, then l and l, and leave o untouched → Result: "ehllo"

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Steps:

• Convert the string into a list to easily swap characters.
• Loop through it with a step of 2 and swap char_list[i] and char_list[i+1].
• Join the result back into a string manually.

def solution(s):
    char_list = list(s)

    for i in range(0, len(char_list) - 1, 2):
        char_list[i], char_list[i + 1] = char_list[i + 1], char_list[i]

    results = ""
    for char in char_list:
        results += char
    return results

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Problem Two: Palindrome Check (No Built-ins)

Task:

Write a function that checks whether a string is a palindrome.

• Case should be ignored (e.g. A == a)
• Non-letter characters should be ignored
• Do not use any built-in string methods (like .lower())

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Explanation

We’re going to:

• Filter only alphabet characters from the string.
• Convert any uppercase letters to lowercase manually using ASCII math.
• Then use a two-pointer technique to check if the string reads the same forward and backward.

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Steps:

• Loop through each character and keep only letters.
• Convert uppercase to lowercase by adding 32 to the ASCII value.
• Compare characters from both ends inward.

def solution(input_string):
    filtered_char = []

    for char in input_string:
        if ('a' <= char <= 'z') or ('A' <= char <= 'Z'):
            if 'A' <= char <= 'Z':
                filtered_char.append(chr(ord(char) + 32))
            else:
                filtered_char.append(char)

    left = 0
    right = len(filtered_char) - 1

    while left < right:
        if filtered_char[left] != filtered_char[right]:
            return False
        left += 1
        right -= 1

    return True

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That's all for today's string manipulation exercises without built-in methods. Keep practicing - repetition and raw logic will sharpen your coding instincts!