Question 1

Consider the following string mySubject:
```python
mySubject = "Computer Science"
What will be the output of the following string operations :
i. print(mySubject[0:len(mySubject)])
ii. print(mySubject[-7:-1])
iii. print(mySubject[::2])
iv. print(mySubject[len(mySubject)-1])
v. print(2*mySubject)
vi. print(mySubject[::-2])
vii. print(mySubject[:3] + mySubject[3:])
viii. print(mySubject.swapcase())
ix. print(mySubject.startsworth('Comp'))
x. print(mySubject.isalpha())

Accepted Answer

Let's analyze each operation step-by-step:

i. print(mySubject[0:len(mySubject)])
- This prints the substring from index 0 to the length of the string (exclusive), which is the entire string.
- Output: 'Computer Science'

ii. print(mySubject[-7:-1])
- Negative indices count from the end. -1 is last character.
- So indices from -7 to -1 (exclusive) correspond to characters from index len(mySubject)-7 to len(mySubject)-1.
- 'Science' is at the end, 'Science' length 7, so -7:-1 extracts 'Scienc'
- Output: 'Scienc'

iii. print(mySubject[::2])
- This slices the string with step 2, i.e., every second character starting from index 0.
- Characters at indices 0,2,4,...
- 'C','m','u','e',' ','c','n','c'
- Output: 'Cmue cnc'

iv. print(mySubject[len(mySubject)-1])
- Prints the last character of the string.
- Last character is 'e'
- Output: 'e'

v. print(2*mySubject)
- Prints the string twice concatenated.
- Output: 'Computer ScienceComputer Science'

vi. print(mySubject[::-2])
- Prints the string reversed with step -2.
- Starting from last character, every second character backwards.
- Characters: 'e','c','n',' ','r','t','m'
- Output: 'ecn rtm'

vii. print(mySubject[:3] + mySubject[3:])
- Concatenates substring from start to 3 and from 3 to end.
- This is the original string.
- Output: 'Computer Science'

viii. print(mySubject.swapcase())
- Swaps case of each character.
- 'Computer Science' becomes 'cOMPUTER sCIENCE'
- Output: 'cOMPUTER sCIENCE'

ix. print(mySubject.startsworth('Comp'))
- There is a typo: 'startswith' is correct method.
- Assuming typo, mySubject.startswith('Comp') returns True because string starts with 'Comp'.
- Output: True

x. print(mySubject.isalpha())
- Checks if all characters are alphabets.
- Since string contains space, returns False.
- Output: False — Each sub-part is explained with Python string slicing and method behavior:
- Slicing with positive and negative indices
- String repetition
- Reversing with step
- Case swapping
- String methods startswith and isalpha

Note: The typo in 'startswith' is noted and corrected in explanation.

Question 2

Consider the following string myAddress:
```python
myAddress = "WZ-1, New Ganga Nagar, New Delhi"
What will be the output of following string operations :
i. print(myAddress.lower())
ii. print(myAddress.upper())
iii. print(myAddress.count('New'))
iv. print(myAddress.find('New'))
v. print(myAddress.rfind('New'))
vi. print(myAddress.split(','))
vii. print(myAddress.split(''))
viii. print(myAddress.replace('New','Old'))
ix. print(myAddress.partition(','))
x. print(myAddress.index('Agra'))

Accepted Answer

Let's analyze each operation step-by-step:

i. print(myAddress.lower())
- Converts all characters to lowercase.
- Output: 'wz-1, new ganga nagar, new delhi'

ii. print(myAddress.upper())
- Converts all characters to uppercase.
- Output: 'WZ-1, NEW GANGA NAGAR, NEW DELHI'

iii. print(myAddress.count('New'))
- Counts occurrences of substring 'New'.
- 'New' appears twice.
- Output: 2

iv. print(myAddress.find('New'))
- Returns index of first occurrence of 'New'.
- 'New' starts at index 5.
- Output: 5

v. print(myAddress.rfind('New'))
- Returns index of last occurrence of 'New'.
- Last 'New' starts at index 19.
- Output: 19

vi. print(myAddress.split(','))
- Splits string at commas.
- Output: ['WZ-1', ' New Ganga Nagar', ' New Delhi']

vii. print(myAddress.split(''))
- Splitting by empty string is invalid and raises ValueError.
- Output: Error: empty separator

viii. print(myAddress.replace('New','Old'))
- Replaces all occurrences of 'New' with 'Old'.
- Output: 'WZ-1, Old Ganga Nagar, Old Delhi'

ix. print(myAddress.partition(','))
- Splits string into tuple at first comma.
- Output: ('WZ-1', ',', ' New Ganga Nagar, New Delhi')

x. print(myAddress.index('Agra'))
- Searches for substring 'Agra'. Not found.
- Raises ValueError: substring not found — Each sub-part is explained with Python string methods:
- lower(), upper() for case conversion
- count() for substring count
- find() and rfind() for substring index
- split() behavior with valid and invalid separators
- replace() for substring replacement
- partition() returns tuple
- index() raises error if substring not found

Note: split('') is invalid and will cause error.

Question 3

Write a function deleteChar() which takes two parameters one is a string and other is a character. The function should create a new string after deleting all occurrences of the character from the string and return the new string.

Accepted Answer

To write the function deleteChar(), follow these steps:

1. Define the function deleteChar() with two parameters: input_string (string) and char_to_delete (character).
2. Initialize an empty string result to store the new string.
3. Loop through each character ch in input_string.
4. If ch is not equal to char_to_delete, append ch to result.
5. After the loop ends, return the result string.

Example implementation in Python:

def deleteChar(input_string, char_to_delete):
    result = ""
    for ch in input_string:
        if ch != char_to_delete:
            result += ch
    return result

Example usage:
input_str = "hello world"
char_del = 'l'
print(deleteChar(input_str, char_del))  # Output: heo word — The function iterates over each character of the input string and constructs a new string by excluding all occurrences of the specified character. This ensures that all instances of the character are removed from the string.

Question 4

Input a string having some digits. Write a function to return the sum of digits present in this string.

Accepted Answer

To find the sum of digits in a string:

1. Define a function sumOfDigits() that takes a string as input.
2. Initialize a variable total_sum to 0.
3. Loop through each character ch in the string.
4. Check if ch is a digit using the isdigit() method.
5. If yes, convert ch to integer and add it to total_sum.
6. After the loop, return total_sum.

Example implementation in Python:

def sumOfDigits(input_string):
    total_sum = 0
    for ch in input_string:
        if ch.isdigit():
            total_sum += int(ch)
    return total_sum

Example usage:
input_str = "abc123xyz"
print(sumOfDigits(input_str))  # Output: 6 (1+2+3) — The function checks each character to determine if it is a digit. If it is, it converts it to an integer and adds it to a running total. This way, the sum of all digits in the string is computed.

Question 5

Write a function that takes a sentence as an input parameter where each word in the sentence is separated by a space. The function should replace each blank with a hyphen and then return the modified sentence.

Accepted Answer

To replace spaces with hyphens in a sentence:

1. Define a function replaceBlanks() that takes a sentence string as input.
2. Use the string method replace() to replace all spaces (' ') with hyphens ('-').
3. Return the modified string.

Example implementation in Python:

def replaceBlanks(sentence):
    return sentence.replace(' ', '-')

Example usage:
sentence = "This is a test"
print(replaceBlanks(sentence))  # Output: This-is-a-test — The replace() method of strings is used to substitute all occurrences of a specified substring (space) with another substring (hyphen). This effectively replaces all blanks with hyphens.

Question 6

Which of the following is NOT a sequence data type introduced in Python Chapter 5?

Accepted Answer

Dictionary — Strings, lists, and tuples are sequence data types introduced in Chapter 5. Dictionary is a mapping data type, not a sequence.

Question 7

Which of the following is a correct way to create a multi-line string in Python?

Accepted Answer

Using triple quotes ''' ''' or """ """ — Triple quotes (either ''' ''' or """ """) allow strings to span multiple lines in Python.

Question 8

In Python, what is the data type of a string of length one?

Accepted Answer

String — Python does not have a separate character data type; a string of length one is still considered a string.

Question 9

What will be the output of the following code?

```python
str1 = 'Hello World!'
print(str1[6])
```

Accepted Answer

W — Indexing starts at 0, so str1[6] accesses the 7th character which is 'W' in 'Hello World!'.

Question 10

What error will be raised if you try to access str1[15] given str1 = 'Hello World!'?

Accepted Answer

IndexError: string index out of range — Accessing an index beyond the string length raises IndexError in Python.

Question 11

Given the string str1 = 'Hello World!', what will be the output of str1[-1]?

Accepted Answer

! — Negative index -1 accesses the last character in the string, which is '!'.

Question 12

Examine the following table representing the string 'Hello World!'. What is the character at positive index 4 and negative index -8 respectively?

| Positive Indices | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| String | H | e | l | l | o |   | W | o | r | l | d | ! |
| Negative Indices | -12 | -11 | -10 | -9 | -8 | -7 | -6 | -5 | -4 | -3 | -2 | -1 |

Accepted Answer

o and o — At positive index 4 is 'o', and at negative index -8 is also 'o' as per the table.

Question 13

What will be the output of the following code?

```python
str1 = 'Hello World!'
print(len(str1))
print(str1[len(str1)-1])
print(str1[-len(str1)])
```

Accepted Answer

12, '!', 'H' — Length of 'Hello World!' is 12; last character at index 11 is '!', and first character at negative index -12 is 'H'.

Question 14

What happens if you try to execute the statement `str1[1] = 'a'` given `str1 = 'Hello World!'`?

Accepted Answer

TypeError is raised because strings are immutable. — Strings in Python are immutable; you cannot change individual characters after creation. Attempting to assign a character raises TypeError.

Question 15

Which operator is used in Python to concatenate two strings?

Accepted Answer

+ — The '+' operator is used to join two strings in Python, producing a new concatenated string.

Strings

Strings — Study Notes

8.1 INTRODUCTION

8.2 STRINGS

8.2.1 Accessing Characters in a String

Practice Questions — Strings

All 11 Chapters in Computer Science