Samacheer Kalvi 12th Computer Science Chapter 8 Strings and String Manipulation Exercise Solutions | KalviGavani

How to Use This Page

1. Attempt every exercise on your own before reading the solution. 2. Compare your approach with the solution — focus on the logic, not just the final answer. 3. Type and run the Python code on your computer; reading alone is not enough. 4. Review the Common Mistakes section to avoid errors that cost marks in exams.

Key Concepts

Important String Methods

Multiple Choice Questions (MCQs)

Q1. What is the output of "Hello"[1:4]?

• (a) "Hel"
• (b) "ell"
• (c) "ello"
• (d) "ell"

Q2. Which method converts "hello world" to "Hello World"?

• (a) upper()
• (b) capitalize()
• (c) title()
• (d) swapcase()

Q3. What does "banana".count("an") return?

• (a) 1
• (b) 2
• (c) 3
• (d) 0

Q4. Strings in Python are:

• (a) Mutable
• (b) Immutable
• (c) Both mutable and immutable
• (d) None of the above

Q5. What is the result of "Python"[-3:]?

• (a) "tho"
• (b) "hon"
• (c) "Pyt"
• (d) Error

Fill in the Blanks

Q1. The ______ method removes leading and trailing whitespace from a string.

Q2. ______ is the escape character for a new line.

Q3. "hello".find("x") returns ______.

Q4. The ______ method joins elements of a list into a single string using a separator.

Q5. "5".zfill(4) returns ______.

True or False

Q1. Strings in Python can be modified using indexing, e.g., s[0] = 'h'.

Q2. "Hello".lower() changes the original string.

Q3. The split() method returns a list.

Q4. Triple quotes can be used to create multi-line strings.

Q5. "123".isdigit() returns True.

Match the Following

Short Answer Questions

Q1. Explain string immutability with an example.

Strings in Python cannot be modified after creation. Any operation that seems to modify a string actually creates a new string.

s = "Hello"
# s[0] = "h"  # TypeError: 'str' object does not support item assignment

# To "change" a string, create a new one:
s = "h" + s[1:]  # Create new string "hello"
print(s)  # hello

The original "Hello" object remains in memory until garbage-collected.

Q2. What is string slicing? Explain with examples.

Slicing extracts a substring using the syntax s[start:stop:step].

s = "Python"
print(s[0:3])    # Pyt  (indices 0,1,2)
print(s[2:])      # thon (from index 2 to end)
print(s[:4])      # Pyth (from start to index 3)
print(s[-3:])     # hon  (last 3 characters)
print(s[::2])     # Pto  (every 2nd character)
print(s[::-1])    # nohtyP (reversed)

Q3. Differentiate between find() and index().

s = "Hello World"
print(s.find("World"))   # 6
print(s.index("World"))  # 6
print(s.find("xyz"))     # -1
# s.index("xyz")         # ValueError: substring not found

Q4. Explain string formatting methods in Python.

Python offers three ways to format strings:

name = "Arun"
marks = 95

# 1. f-string (Python 3.6+, recommended)
print(f"{name} scored {marks}")  # Arun scored 95

# 2. format() method
print("{} scored {}".format(name, marks))  # Arun scored 95
print("{0} scored {1}".format(name, marks))  # Arun scored 95
print("{n} scored {m}".format(n=name, m=marks))  # Arun scored 95

# 3. %-formatting (older style)
print("%s scored %d" % (name, marks))  # Arun scored 95

Q5. List the escape characters in Python.

print("Line1\nLine2")    # Prints on two lines
print("A\tB\tC")         # Prints with tabs
print("She said \"Hi\"") # Prints: She said "Hi"

Detailed Answers

Q1. Write a Python program to check whether a string is a palindrome.

def is_palindrome(s):
    """Check if a string is a palindrome."""
    s = s.lower().replace(" ", "")  # normalize
    return s == s[::-1]

# Method 1: Using slicing
word = input("Enter a string: ")
if is_palindrome(word):
    print(word, "is a palindrome")
else:
    print(word, "is not a palindrome")

# Method 2: Using loop (manual comparison)
def is_palindrome_loop(s):
    s = s.lower().replace(" ", "")
    left, right = 0, len(s) - 1
    while left < right:
        if s[left] != s[right]:
            return False
        left += 1
        right -= 1
    return True

Test: "madam" → True, "hello" → False, "racecar" → True

Q2. Write a program to count the number of vowels, consonants, digits, and special characters in a string.

def count_chars(s):
    """Count vowels, consonants, digits, and special characters."""
    vowels = "aeiouAEIOU"
    v = c = d = sp = 0
    for char in s:
        if char.isalpha():
            if char in vowels:
                v += 1
            else:
                c += 1
        elif char.isdigit():
            d += 1
        elif char != " ":
            sp += 1
    return v, c, d, sp

s = input("Enter a string: ")
v, c, d, sp = count_chars(s)
print(f"Vowels: {v}")
print(f"Consonants: {c}")
print(f"Digits: {d}")
print(f"Special characters: {sp}")

Q3. Write a program to reverse each word in a sentence while keeping word order.

sentence = input("Enter a sentence: ")
words = sentence.split()
reversed_words = [word[::-1] for word in words]
result = " ".join(reversed_words)
print("Original:", sentence)
print("Reversed words:", result)

# Input: Hello World Python
# Output: olleH dlroW nohtyP

Q4. Write a program to remove all duplicate characters from a string while preserving order.

def remove_duplicates(s):
    """Remove duplicate characters, preserving first occurrence order."""
    seen = set()
    result = ""
    for char in s:
        if char not in seen:
            seen.add(char)
            result += char
    return result

s = input("Enter a string: ")
print("After removing duplicates:", remove_duplicates(s))
# Input: "programming" → Output: "progamin"

Q5. Write a program to check if two strings are anagrams of each other.

def are_anagrams(s1, s2):
    """Check if two strings are anagrams."""
    s1 = s1.lower().replace(" ", "")
    s2 = s2.lower().replace(" ", "")
    return sorted(s1) == sorted(s2)

str1 = input("Enter first string: ")
str2 = input("Enter second string: ")

if are_anagrams(str1, str2):
    print("The strings are anagrams")
else:
    print("The strings are not anagrams")
# Input: "listen", "silent" → Anagrams
# Input: "hello", "world" → Not anagrams

Q6. Write a program to find the most frequent character in a string.

def most_frequent(s):
    """Find the most frequent character in a string."""
    freq = {}
    for char in s:
        if char != " ":
            freq[char] = freq.get(char, 0) + 1
    max_char = max(freq, key=freq.get)
    return max_char, freq[max_char]

s = input("Enter a string: ")
char, count = most_frequent(s)
print(f"Most frequent character: '{char}' appears {count} times")
# Input: "programming" → 'g' and 'r' and 'm' each appear twice
# The max() returns the first one encountered

Q7. Write a program to convert between different string cases.

s = "hello World PYTHON"

print("Original:       ", s)
print("upper():        ", s.upper())        # HELLO WORLD PYTHON
print("lower():        ", s.lower())        # hello world python
print("title():        ", s.title())        # Hello World Python
print("capitalize():   ", s.capitalize())   # Hello world python
print("swapcase():     ", s.swapcase())     # HELLO wORLD python

Common Mistakes

Exam Checklist

• [ ] I can use indexing and slicing on strings (positive and negative indices)
• [ ] I can explain string immutability and work around it
• [ ] I know all key string methods: upper, lower, find, replace, split, join, strip, count, isalpha, isdigit, isalnum
• [ ] I can format strings using f-strings, .format(), and %-formatting
• [ ] I understand escape characters (\n, \t, \\, \', \")
• [ ] I can write programs for palindrome check, character counting, word reversal
• [ ] I can differentiate find() vs index(), split() vs join()
• [ ] I can trace string operations and predict outputs correctly