Strings — NCERT Solutions

Given: mySubject = "Computer Science"

The string has 16 characters (indices 0 to 15).

$$\text{C o m p u t e r S c i e n c e}$$
$$\text{0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15}$$

i. print(mySubject[0:len(mySubject)])

len(mySubject) = 16, so mySubject[0:16] returns the entire string.

Output:

Computer Science

ii. print(mySubject[-7:-1])

Negative index $-7$ corresponds to index $16 - 7 = 9$ (character S) and $-1$ corresponds to index $15$ (exclusive), so characters at indices 9 to 14 are returned: S, c, i, e, n, c.

Output:

Scienc

iii. print(mySubject[::2])

Slice with step 2 picks every alternate character starting from index 0:

• Indices: 0(C), 2(m), 4(u), 6(e), 8( ), 10(c), 12(e), 14(c)

Output:

Cmue ce

iv. print(mySubject[len(mySubject)-1])

len(mySubject) - 1 = 15, so mySubject[15] = 'e' (last character).

Output:

e

**v. print(2*mySubject)**

The * operator repeats the string 2 times.

Output:

Computer ScienceComputer Science

vi. print(mySubject[::-2])

Slice with step $-2$ starts from the last character (index 15) and moves backwards picking every alternate character:

• Indices: 15(e), 13(n), 11(i), 9(S), 7(r), 5(t), 3(p), 1(o)

Output:

eniSrtpo

vii. print(mySubject[:3] + mySubject[3:])

mySubject[:3] = "Com" and mySubject[3:] = "puter Science". Concatenating them gives back the full string.

Output:

Computer Science

viii. print(mySubject.swapcase())

swapcase() converts uppercase letters to lowercase and vice versa.

• C → c, o → O, m → M, p → P, u → U, t → T, e → E, r → R, space stays, S → s, c → C, i → I, e → E, n → N, c → C, e → E

Output:

cOMPUTER sCIENCE

ix. print(mySubject.startswith('Comp'))

startswith() returns True if the string starts with the given prefix. "Computer Science" does start with "Comp".

(Note: The question has a typo startsworth; the correct method is startswith.)

Output:

True

x. print(mySubject.isalpha())

isalpha() returns True only if all characters are alphabetic. "Computer Science" contains a space, so it returns False.

Output:

False

Given: myAddress = "WZ-1, New Ganga Nagar, New Delhi"

i. print(myAddress.lower())

lower() converts all characters to lowercase.

Output:

wz-1, new ganga nagar, new delhi

ii. print(myAddress.upper())

upper() converts all characters to uppercase.

Output:

WZ-1, NEW GANGA NAGAR, NEW DELHI

iii. print(myAddress.count('New'))

count() returns the number of non-overlapping occurrences of the substring 'New' in the string. 'New' appears at positions corresponding to "New Ganga" and "New Delhi" — twice.

Output:

2

iv. print(myAddress.find('New'))

find() returns the index of the first occurrence of the substring.

Counting characters in "WZ-1, New Ganga Nagar, New Delhi":

• W=0, Z=1, -=2, 1=3, ,=4, =5, N=6

First 'New' starts at index 6.

Output:

6

v. print(myAddress.rfind('New'))

rfind() returns the index of the last occurrence of the substring.

Counting: "WZ-1, New Ganga Nagar, " has 23 characters (indices 0–22), so the second 'New' starts at index 23.

Output:

23

vi. print(myAddress.split(','))

split(',') splits the string at every comma and returns a list.

Output:

['WZ-1', ' New Ganga Nagar', ' New Delhi']

vii. print(myAddress.split(' '))

split(' ') splits the string at every single space and returns a list.

Output:

['WZ-1,', 'New', 'Ganga', 'Nagar,', 'New', 'Delhi']

viii. print(myAddress.replace('New', 'Old'))

replace('New', 'Old') replaces all occurrences of 'New' with 'Old'.

Output:

WZ-1, Old Ganga Nagar, Old Delhi

ix. print(myAddress.partition(','))

partition(',') splits the string at the first occurrence of ',' and returns a tuple of three parts: (before separator, separator, after separator).

Output:

('WZ-1', ',', ' New Ganga Nagar, New Delhi')

x. print(myAddress.index('Agra'))

index() raises a ValueError if the substring is not found. 'Agra' does not exist in myAddress.

Output:

ValueError: substring not found

Concept Used:

• input() to read lines until an empty line (Enter) is pressed.
• String methods isalpha(), isdigit() to classify characters.
• A character that is neither alphabetic nor a digit nor a space is a special symbol.
• Words are counted by splitting on spaces.

Program:

total_chars = 0
total_alpha = 0
total_digits = 0
total_special = 0
total_words = 0

print("Enter lines of text (press Enter on empty line to stop):")

while True:
    line = input()
    if line == "":          # Stop when user presses Enter on empty line
        break
    total_chars += len(line)
    for ch in line:
        if ch.isalpha():
            total_alpha += 1
        elif ch.isdigit():
            total_digits += 1
        elif ch == ' ':
            pass            # spaces counted in total_chars but not special
        else:
            total_special += 1
    # Count words (each word separated by one space)
    words = line.split(' ')
    # Remove empty strings caused by leading/trailing spaces
    words = [w for w in words if w != '']
    total_words += len(words)

print("Total characters (including spaces):", total_chars)
print("Total alphabets                     :", total_alpha)
print("Total digits                        :", total_digits)
print("Total special symbols               :", total_special)
print("Total words                         :", total_words)

Sample Run:

Enter lines of text (press Enter on empty line to stop):
Hello World 123!

Total characters (including spaces): 16
Total alphabets                     : 10
Total digits                        : 3
Total special symbols               : 1
Total words                         : 3

Concept Used:

• Split the string into individual words using split().
• Capitalise the first letter of each word using capitalize() (or manually using indexing).
• Join the words back using join().

Program:

def toTitleCase(sentence):
    """
    Converts a string to title case.
    Parameter: sentence (str) - input string
    Returns  : title-cased string
    """
    words = sentence.split()          # Split on whitespace
    title_words = []
    for word in words:
        # Capitalise first letter, lowercase the rest
        title_word = word[0].upper() + word[1:].lower()
        title_words.append(title_word)
    return ' '.join(title_words)

# --- Driver code ---
text = input("Enter a string: ")
result = toTitleCase(text)
print("Title Case String:", result)

Sample Run:

Enter a string: hello world from python
Title Case String: Hello World From Python

Note: Python also provides a built-in str.title() method, but the above function demonstrates the logic manually as expected in a board exam.