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Chapter 10

String Manipulation

Class 11 - Computer Science with Python Sumita Arora


Multiple Choice Questions

Question 1

Negative index -1 belongs to .......... of string.

  1. first character
  2. last character ✓
  3. second last character
  4. second character

Question 2

Which of the following is/are not legal string operators?

  1. in
  2. +
  3. *
  4. / ✓

Question 3

Which of the following functions will return the total number of characters in a string?

  1. count()
  2. index()
  3. len() ✓
  4. all of these

Question 4

Which of the following functions will return the last three characters of a string s?

  1. s[3:]
  2. s[:3]
  3. s[-3:] ✓
  4. s[:-3]

Question 5

Which of the following functions will return the first three characters of a string s?

  1. s[3:]
  2. s[:3] ✓
  3. s[-3:]
  4. s[:-3]

Question 6

Which of the following functions will return the string in all caps?

  1. upper() ✓
  2. toupper()
  3. isupper()
  4. to-upper()

Question 7

Which of the following functions will return the string with every 'P' replaced with a 'z'?

  1. find()
  2. index()
  3. replace() ✓
  4. split()

Question 8

Which of the following functions will return a list containing all words of the string?

  1. find()
  2. index()
  3. partition()
  4. split() ✓

Question 9

Which of the following functions will always return a tuple of 3 elements?

  1. find()
  2. index()
  3. partition() ✓
  4. split()

Question 10

What is the output of the following code?

str1 = "Mission 999"
str2 = "999"
print(str1.isdigit(),str2.isdigit())
  1. False True ✓
  2. False False
  3. True False
  4. True True

Question 11

Choose the correct function to get the ASCII code of a character.

  1. char('char')
  2. ord('char') ✓
  3. ascii('char')
  4. All of these

Question 12

Which method should I use to convert String "Python programming is fun" to "Python Programming Is Fun" ?

  1. capitalize()
  2. title() ✓
  3. istitle()
  4. upper()

Question 13

Guess the correct output of the following String operations.

str1 = 'Wah'
print(str1*2)
  1. WahWah ✓
  2. TypeError: unsupported operand type(s) for * : 'str' and 'int'
  3. WWaahh
  4. Wah2

Question 14

What is the output of the following string operation?

str = "My roll no. is 12"
print(str.isalnum())
  1. True
  2. False ✓
  3. Error
  4. No output

Question 15

Select the correct output of the following String operations.

str1 = 'Waha'
print(str1[:3] + 'Bhyi' + str1[-3:])
  1. Wah Bhyi Wah
  2. WahBhyiaha ✓
  3. WahBhyiWah
  4. WahBhyiWaha

Question 16

Select the correct output of the following String operations.

str = "my name is Anu John"
print(str.capitalize())
  1. 'My name is anu john' ✓
  2. TypeError: unsupported operand type(s) for * : 'str' and 'int'
  3. 'My name is Anu John'
  4. 'My Name Is Anu John'

Question 17

Choose the correct function to get the character from ASCII number.

  1. ascii(number)
  2. char(number)
  3. chr(number) ✓
  4. all of these

Question 18

s = ' '(single space). Then s.isalnum() will return.

  1. True
  2. False ✓
  3. Error
  4. nothing

Question 19

Which of the following functions removes all leading and trailing spaces from a string?

  1. lstrip()
  2. rstrip()
  3. strip() ✓
  4. all of these

Question 20

Which of the following functions will raise an error if the given substring is not found in the string?

  1. find()
  2. index() ✓
  3. replace()
  4. all of these

Fill in the Blanks

Question 1

The string indexes begin 0 onwards.

Question 2

For strings, + operator performs concatenation.

Question 3

For strings, * operator performs replication.

Question 4

The in and not in are membership operators for strings (in, not in).

Question 5

The ord() returns the ASCII value of a given character.

Question 6

If a string contains letters and digits, function isalnum() will return true.

Question 7

'ab'.isalpha() will return value as True.

Question 8

To get each word's first letter capitalized, title() function is used.

Question 9

Function index() raises an exception if the substring is not found.

Question 10

Function split() divides a line of text into individual words.

True/False Questions

Question 1

Strings have both positive and negative indexes.
True

Question 2

Python does not support a character type; a single character is treated as strings of length one.
True

Question 3

Strings are immutable in Python, which means a string cannot be modified.
True

Question 4

Like '+', all other arithmetic operators are also supported by strings.
False

Question 5

Functions capitalize() and title() return the same result.
False

Question 6

Functions partition() and split() work identically.
False

Question 7

The find() and index() are similar functions.
True

Question 8

The find() does not raise an exception if the substring is not found.
True

Question 9

The partition() function's result is always a 3-element tuple.
True

Question 10

The split() returns always a 3-element list.
False

Type A : Short Answer Questions/Conceptual Questions

Question 1

Write a Python script that traverses through an input string and prints its characters in different lines — two characters per line.

Answer

str = input("Enter the string: ")
length = len(str)
for a in range(0, length, 2):
    print(str[a:a+2])

Output

Enter the string: KnowledgeBoat
Kn
ow
le
dg
eB
oa
t

Question 2

Out of the following operators, which ones can be used with strings in Python?

=, -, *, /, //, %, >, <>, in, not in, <=

Answer

The following Python operators can be used with strings:

=, *, >, in, not in, <=

Question 3

What is the result of following statement, if the input is 'Fun'?

print(input("...") + "trial" + "Ooty" * 3)

Answer

The result of the statement is:

FuntrialOotyOotyOoty

Question 4

Which of the following is not a Python legal string operation?

(a) 'abc' + 'abc'
(b) 'abc' * 3
(c) 'abc' + .3
(d) 'abc.lower()

Answer

'abc' + .3 is not a legal string operation in Python. The operands of + operator should be both string or both numeric. Here one operand is string and other is numeric. This is not allowed in Python.

Question 5

Can you say strings are character lists? Why? Why not?

Answer

Strings are sequence of characters where each character has a unique index. This implies that strings are iterable like lists but unlike lists they are immutable so they cannot be modified at runtime. Therefore, strings can't be considered as character lists. For example,

str = 'cat'
# The below statement
# is INVALID as strings
# are immutable
str[0] = 'b' 

# Considering character lists
strList = ['c', 'a', 't']
# The below statement
# is VALID as lists
# are mutable
strList[0] = 'b'

Question 6

Given a string S = "CARPE DIEM". If n is length/2 (length is the length of the given string), then what would following return?

(a) S[: n]
(b) S[n :]
(c) S[n : n]
(d) S[1 : n]
(e) S[n : length - 1]

Answer

(a) CARPE
(b) DIEM
(c) (Empty String)
(d) ARPE
(e) DIE

Question 7

From the string S = "CARPE DIEM", which ranges return "DIE" and "CAR"?

Answer

  1. S[6:9] returns DIE
  2. S[:3] returns CAR

Question 8

What happens when from a string slice you skip the start and/or end values of the slice?

Answer

If start value is skipped, it is assumed as 0 i.e. the slice begins from the start of the string.

If end value is skipped, it is assumed as the last index of the string i.e. the slice extends till the end of the string.

Question 9

What would the following expressions return?

  1. "Hello World".upper( ).lower( )
  2. "Hello World".lower( ).upper( )
  3. "Hello World".find("Wor", 1, 6)
  4. "Hello World".find("Wor")
  5. "Hello World".find("wor")
  6. "Hello World".isalpha( )
  7. "Hello World".isalnum( )
  8. "1234".isdigit( )
  9. "123FGH".isdigit( )

Answer

  1. hello world
  2. HELLO WORLD
  3. -1
  4. 6
  5. -1
  6. False
  7. False
  8. True
  9. False

Explanation

  1. upper() first converts all letters of "Hello World" to uppercase. Then "HELLO WORLD".lower() converts all letters to lowercase.
  2. lower() first converts all letters of "Hello World" to lowercase. Then "hello world".upper() converts all letters to uppercase.
  3. "Hello World".find("Wor", 1, 6) searches for the presence of substring "Wor" between 1 and 6 indexes of string "Hello World". Substring from 1 to 6 index is "ello W". As "Wor" is not present in this hence the result is False.
  4. "Hello World".find("Wor") searches for the presence of substring "Wor" in the entire "Hello World" string. Substring "Wor" starts at index 6 of "Hello World" hence the result is 6.
  5. "Hello World".find("wor") searches for the presence of substring "wor" in the entire "Hello World" string. find() performs case sensitive search so "wor" and "Wor" are different hence the result is -1.
  6. "Hello World".isalpha( ) checks if all characters in the string as alphabets. As a space is also present in the string hence it returns False.
  7. "Hello World".isalnum( ) checks if all characters in the string are either alphabets or digits. As a space is also present in the string which is neither an alphabet nor a string hence it returns False.
  8. "1234".isdigit( ) checks if all characters in the string are digits or not. As all characters are digits hence the result is True.
  9. As "FGH" in the string "123FGH" are not digits hence the result is False.

Question 10

Which functions would you choose to use to remove leading and trailing white spaces from a given string?

Answer

lstrip() removes leading white-spaces, rstrip() removes trailing white-spaces and strip() removes leading and trailing white-spaces from a given string.

Question 11

Try to find out if for any case, the string functions isalnum( ) and isalpha( ) return the same result

Answer

isalnum( ) and isalpha( ) return the same result in the following cases:

  1. If string contains only alphabets then both isalnum( ) and isalpha( ) return True. For example, "Hello".isalpha() and "Hello".isalnum() return True.
  2. If string contains only special characters and/or white-spaces then both isalnum( ) and isalpha( ) return False. For example, "*#".isalpha() and "*#".isalnum() return False.

Question 12

Suggest appropriate functions for the following tasks:

  1. To check whether the string contains digits
  2. To find for the occurrence a string within another string
  3. To convert the first letter of a string to upper case
  4. to capitalize all the letters of the string
  5. to check whether all letters of the string are in capital letters
  6. to remove from right of a string all string-combinations from a given set of letters
  7. to remove all white spaces from the beginning of a string

Answer

  1. isdigit()
  2. find()
  3. capitalize()
  4. upper()
  5. isupper()
  6. rstrip(characters)
  7. lstrip()

Question 13

In a string slice, the start and end values can be beyond limits. Why?

Answer

String slicing always returns a subsequence and empty subsequence is a valid sequence. Thus, when a string is sliced outside the bounds, it still can return empty subsequence and hence Python gives no errors and returns empty subsequence.

Question 14

Can you specify an out of bound index when accessing a single character from a string? Why?

Answer

We cannot specify an out of bound index when accessing a single character from a string, it will cause an error. When we use an index, we are accessing a constituent character of the string. If the index is out of bounds there is no character to return from the given index hence Python throws string index out of range error.

Question 15

Can you add two strings? What effect does ' + ' have on strings?

Answer

Yes two strings can be added using the '+' operator. '+' operator concatenates two strings.

Type B: Application Based Questions

Question 1a

What is the result of the following expression?

print("""
1
 2
  3
""")

Answer


1
 2
  3

Question 1b

What is the result of the following expression?

text = "Test.\nNext line."
print (text)

Answer

Test.
Next line.

Question 1c

What is the result of the following expression?

print ('One', ' Two ' * 2)
print ('One ' + 'Two' * 2)
print (len('10123456789'))

Answer

One  Two  Two 
One TwoTwo
11

Question 1d

What is the result of the following expression?

s = '0123456789'
print(s[3], ", ", s[0 : 3], " - ", s[2 : 5])
print(s[:3], " - ", s[3:], ", ", s[3:100])
print(s[20:], s[2:1], s[1:1])

Answer

3 ,  012  -  234
012  -  3456789 ,  3456789

Question 1e

What is the result of the following expression?

s ='987654321'
print (s[-1], s[-3])
print (s[-3:], s[:-3])
print (s[-100:-3], s[-100:3])

Answer

1 3
321 987654
987654 987

Question 2a

What will be the output produced by following code fragments?

y = str(123)
x = "hello" * 3
print (x, y)
x = "hello" + "world"
y = len(x)
print (y, x)

Answer

Output
hellohellohello 123
10 helloworld
Explanation

str(123) converts the number 123 to string and stores in y so y becomes "123". "hello" * 3 repeats "hello" 3 times and stores it in x so x becomes "hellohellohello".

"hello" + "world" concatenates both the strings so x becomes "helloworld". As "helloworld" contains 10 characters so len(x) returns 10.

Question 2b

What will be the output produced by following code fragments?

x = "hello" + \
"to Python" + \
"world"
for char in x :
    y = char
    print (y, ' : ', end = ' ')

Answer

Output
h  :  e  :  l  :  l  :  o  :  t  :  o  :     :  P  :  y  :  t  :  h  :  o  :  n  :  w  :  o  :  r  :  l  :  d  : 
Explanation

Inside the for loop, we are traversing the string "helloto Pythonworld" character by character and printing each character followed by a colon (:).

Question 2c

What will be the output produced by following code fragments?

x = "hello world"
print (x[:2], x[:-2], x[-2:])
print (x[6], x[2:4])
print (x[2:-3], x[-4:-2])

Answer

Output
he hello wor ld
w ll
llo wo or
Explanation

x[:2] ⇒ he
x[:-2] ⇒ hello wor
x[-2:] ⇒ ld

x[6] ⇒ w
x[2:4] ⇒ ll

x[2:-3] ⇒ llo wo
x[-4:-2] ⇒ or

Question 3

Carefully go through the code given below and answer the questions based on it :

theStr = " This is a test "         
inputStr = input(" Enter integer: ")
inputlnt = int(inputStr)            
testStr = theStr
while inputlnt >= 0 :               
    testStr = testStr[1:-1]        
    inputlnt = inputlnt - 1
testBool = 't' in testStr
print (theStr)             # Line 1 
print (testStr)            # Line 2 
print (inputlnt)           # Line 3 
print (testBool)           # Line 4 

(i) Given the input integer 3, what output is produced by Line 1?

  1. This is a test
  2. This is a
  3. is a test
  4. is a
  5. None of these

Answer

Option 1 — This is a test

(ii) Given the input integer 3, what output is produced by Line 2?

  1. This is a test
  2. s is a t
  3. is a test
  4. is a
  5. None of these

Answer

Option 2 — s is a t

Explanation

As input is 3 and inside the while loop, inputlnt decreases by 1 in each iteration so the while loop executes 4 times for inputlnt values 3, 2, 1, 0.

1st Iteration
testStr = "This is a test"

2nd Iteration
testStr = "his is a tes"

3rd Iteration
testStr = "is is a te"

4th Iteration
testStr = "s is a t"

(iii) Given the input integer 2, what output is produced by Line 3?

  1. 0
  2. 1
  3. 2
  4. 3
  5. None of these

Answer

Option 5 — None of these

Explanation

Value of inputlnt will be -1 as till inputlnt >= 0 the while loop will continue executing.

(iv) Given the input integer 2, what output is produced by Line 4?

  1. False
  2. True
  3. 0
  4. 1
  5. None of these

Answer

Option 2 — True

Explanation

As input is 2 and inside the while loop, inputlnt decreases by 1 in each iteration so the while loop executes 3 times for inputlnt values 2, 1, 0.

1st Iteration
testStr = "This is a test"

2nd Iteration
testStr = "his is a tes"

3rd Iteration
testStr = "is is a te"

After the while loop finishes executing, value of testStr is "is is a te". 't' in testStr returns True as letter t is present in testStr.

Question 4

Carefully go through the code given below and answer the questions based on it :

testStr = "abcdefghi"                    
inputStr = input ("Enter integer:")      
inputlnt = int(inputStr)                 
count = 2                                
newStr = ''                               
while count <= inputlnt :                
    newStr = newStr + testStr[0 : count]
    testStr = testStr[2:]      #Line 1   
    count = count + 1                    
print (newStr)                 # Line 2
print (testStr)                # Line 3  
print (count)                  # Line 4  
print (inputlnt)               # Line 5  

(i) Given the input integer 4, what output is produced by Line 2?

  1. abcdefg
  2. aabbccddeeffgg
  3. abcdeefgh
  4. ghi
  5. None of these

Answer

Option 3 — abcdeefgh

Explanation

Input integer is 4 so while loop will execute 3 times for values of count as 2, 3, 4.

1st Iteration
    newStr = newStr + testStr[0:2]
⇒ newStr = '' + ab
⇒ newStr = ab

    testStr = testStr[2:]
⇒ testStr = cdefghi

2nd Iteration
    newStr = newStr + testStr[0:3]
⇒ newStr = ab + cde
⇒ newStr = abcde

    testStr = testStr[2:]
⇒ testStr = efghi

3rd Iteration
    newStr = newStr + testStr[0:4]
⇒ newStr = abcde + efgh
⇒ newStr = abcdeefgh

    testStr = testStr[2:]
⇒ testStr = ghi

(ii) Given the input integer 4, what output is produced by Line 3?

  1. abcdefg
  2. aabbccddeeffgg
  3. abcdeefgh
  4. ghi
  5. None of these

Answer

Option 4 — ghi

Explanation

Input integer is 4 so while loop will execute 3 times for values of count as 2, 3, 4.

1st Iteration
    testStr = testStr[2:]
⇒ testStr = cdefghi

2nd Iteration
    testStr = testStr[2:]
⇒ testStr = efghi

3rd Iteration
    testStr = testStr[2:]
⇒ testStr = ghi

(iii) Given the input integer 3, what output is produced by Line 4?

  1. 0
  2. 1
  3. 2
  4. 3
  5. None of these

Answer

Option 5 — None of these

Explanation

Looking at the condition of while loop — while count <= inputlnt, the while loop will stop executing when count becomes greater than inputlnt. Value of inputlnt is 3 so when loop stops executing count will be 4.

(iv) Given the input integer 3, what output is produced by Line 5?

  1. 0
  2. 1
  3. 2
  4. 3
  5. None of these

Answer

Option 4 — 3

Explanation

The input is converted from string to integer and after that its value is unchanged in the code so line 5 prints the input integer 3.

(v) Which statement is equivalent to the statement found in Line 1?

  1. testStr = testStr[2:0]
  2. testStr = testStr[2:-1]
  3. testStr = testStr[2:-2]
  4. testStr = testStr - 2
  5. None of these

Answer

Option 5 — None of these

Question 5

Carefully go through the code given below and answer the questions based on it :

inputStr = input(" Give me a string:")
biglnt = 0
littlelnt = 0
otherlnt = 0
for ele in inputStr:
    if ele >= 'a' and ele <= 'm':     # Line 1
        littlelnt = littlelnt + 1
    elif ele > 'm' and ele <= 'z':
        biglnt = biglnt + 1
    else:
        otherlnt = otherlnt + 1
print (biglnt)             # Line 2
print (littlelnt)          # Line 3
print (otherlnt)           # Line 4
print (inputStr.isdigit()) # Line 5

(i) Given the input abcd what output is produced by Line 2?

  1. 0
  2. 1
  3. 2
  4. 3
  5. 4

Answer

Option 1 — 0

Explanation

In the input abcd, all the letters are between a and m so the condition — if ele >= 'a' and ele <= 'm' is always true. Hence, biglnt is 0.

(ii) Given the input Hi Mom what output is produced by Line 3?

  1. 0
  2. 1
  3. 2
  4. 3
  5. None of these

Answer

Option 3 — 2

Explanation

In the input Hi Mom, only two letters i and m satisfy the condition — if ele >= 'a' and ele <= 'm'. Hence, value of littlelnt is 2.

(iii) Given the input Hi Mom what output is produced by Line 4?

  1. 0
  2. 1
  3. 2
  4. 3
  5. None of these

Answer

Option 4 — 3

Explanation

In the input Hi Mom, 3 characters H, M and space are not between a and z. So for these 3 characters the statement in else part — otherlnt = otherlnt + 1 is executed. Hence, value of otherlnt is 3.

(iv) Given the input 1+2 =3 what output is produced by Line 5?

  1. 0
  2. 1
  3. True
  4. False
  5. None of these

Answer

Option 4 — False

Explanation

As all characters in the input string 1+2 =3 are not digits hence isdigit() returns False.

(v) Give the input Hi Mom, what changes result from modifying Line 1 from

if ele >= 'a' and ele <='m' to the expression
if ele >= 'a' and ele < 'm'?

  1. No change
  2. otherlnt would be larger
  3. littlelnt would be larger
  4. biglnt would be larger
  5. None of these

Answer

Option 2 — otherlnt would be larger

Explanation

For letter m, now else case will be executed increasing the value of otherlnt.

Question 6

Carefully go through the code given below and answer the questions based on it :

in1Str = input(" Enter string of digits: ")
in2Str = input(" Enter string of digits: ")

if len(in1Str)>len(in2Str):
    small = in2Str
    large = in1Str
else:
    small = in1Str
    large = in2Str
newStr = ''
for element in small:
    result = int(element) + int(large[0])
    newStr = newStr + str(result)
    large = large[1:]
print (len(newStr))      # Line 1
print (newStr)           # Line 2
print (large)            # Line 3
print (small)            # Line 4

(i) Given a first input of 12345 and a second input of 246, what result is produced by Line 1?

  1. 1
  2. 3
  3. 5
  4. 0
  5. None of these

Answer

Option 2 — 3

Explanation

As length of smaller input is 3, for loop executes 3 times so 3 characters are added to newStr. Hence, length of newStr is 3.

(ii) Given a first input of 12345 and a second input of 246, what result is produced by Line 2?

  1. 369
  2. 246
  3. 234
  4. 345
  5. None of these

Answer

Option 1 — 369

Explanation

For loop executes 3 times as length of smaller input is 3.

1st Iteration
    result = 2 + 1
⇒ result = 3

    newStr = '' + '3'
⇒ newStr = '3'

    large = 2345

2nd Iteration
    result = 4 + 2
⇒ result = 6

    newStr = '3' + '6'
⇒ newStr = '36'

    large = 345

3rd Iteration
    result = 6 + 3
⇒ result = 9

    newStr = '36' + '9'
⇒ newStr = '369'

    large = 45

Final value of newStr is '369'.

(iii) Given a first input of 123 and a second input of 4567, what result is produced by Line 3?

  1. 3
  2. 7
  3. 12
  4. 45
  5. None of these

Answer

Option 2 — 7

Explanation

For loop executes 3 times as length of smaller input is 3. Initial value of large is 4567.

1st Iteration
    large = large[1:]
⇒ large = 567

2nd Iteration     large = large[1:]
⇒ large = 67

3rd Iteration     large = large[1:]
⇒ large = 7

(iv) Given a first input of 123 and a second input of 4567, what result is produced by Line 4?

  1. 123
  2. 4567
  3. 7
  4. 3
  5. None of these

Answer

Option 1 — 123

Explanation

As length of 123 is less than length of 4567 so 123 is assigned to variable small and gets printed in line 4.

Question 7a

Find the output if the input string is 'Test'.

S = input("Enter String :")
RS = " "
for ch in S :
    RS = ch + RS
print(S + RS)

Answer

Output
TesttseT
Explanation

The for loop reverses the input string and stores the reversed string in variable RS. After that original string and reversed string are concatenated and printed.

Question 7b

Find the output if the input string is 'Test'.

S = input("Enter String :")
RS = " "
for ch in S :
    RS = ch + 2 + RS
print(S + RS)

Answer

The program gives an error at line RS = ch + 2 + RS. The operands to + are a mix of string and integer which is not allowed in Python.

Question 8a

Find the errors. Find the line numbers causing errors.

  1. S = "PURA VIDA"
  2. print(S[9] + S[9 : 15])

Answer

The error is in line 2. Length of string S is 9 so its indexes range for 0 to 8. S[9] is causing error as we are trying to access out of bound index.

Question 8b

Find the errors. Find the line numbers causing errors.

  1. S = "PURA VIDA"
  2. S1 = S[: 10] +S[10 :]
  3. S2 = S[10] + S[-10]

Answer

The error is in line 3. Length of string S is 9 so its forward indexes range for 0 to 8 and backwards indexes range from -1 to -9. S[10] and S[-10] are trying to access out of bound indexes.

Question 8c

Find the errors. Find the line numbers causing errors.

  1. S = "PURA VIDA"
  2. S1 = S * 2
  3. S2 = S1[-19] + S1[-20]
  4. S3 = S1[-19 :]

Answer

The error is in line 3. S1[-19] and S1[-20] are trying to access out of bound indexes.

Question 8d

Find the errors. Find the line numbers causing errors.

  1. S = "PURA VIDA"
  2. S1 = S[: 5]
  3. S2 = S[5 :]
  4. S3 = S1 * S2
  5. S4 = S2 + '3'
  6. S5 = S1 + 3

Answer

The errors are in line 4 and line 6. Two strings cannot be multiplied. A string and an integer cannot be added.

Question 9

What is the output produced?

(i) >>> "whenever" .find("never")

(ii) >>> "whenever" .find("what")

Answer

(i) 3
The starting index of substring "never" in "whenever" is 3.

(ii) -1
Substring "what" is not present in "whenever".

Question 10

What is the output produced?

(i) >>> "-".join(['123','365','1319'])

(ii) >>> " ".join(['Python', 'is', 'fun'])

Answer

(i) '123-365-1319'

(ii) 'Python is fun'

Question 11

Given a string S, write expressions to print

  1. first five characters of S
  2. Ninth character of S
  3. reversed S
  4. alternate characters from reversed S

Answer

  1. print(S[:5])
  2. print(S[8])
  3. for a in range(-1, (-len(S) - 1), -1) :
          print(S[a], end = '')
  4. for a in range(-1, (-len(S) - 1), -2) :
          print(S[a], end = '')

Type C: Programming Practice/Knowledge based Questions

Question 1

Write a program to count the number of times a character occurs in the given string.

Solution
str = input("Enter the string: ")
ch = input("Enter the character to count: ");
c = str.count(ch)
print(ch, "occurs", c, "times")
Output
Enter the string: KnowledgeBoat
Enter the character to count: e
e occurs 2 times

Question 2

Write a program which replaces all vowels in the string with '*'.

Solution
str = input("Enter the string: ")
newStr = ""
for ch in str : 
    lch = ch.lower()
    if lch == 'a' \
       or lch == 'e' \
       or lch == 'i' \
       or lch == 'o' \
       or lch == 'u' :
        newStr += '*'
    else :
        newStr += ch
print(newStr)
Output
Enter the string: Computer Studies
C*mp*t*r St*d**s

Question 3

Write a program which reverses a string and stores the reversed string in a new string.

Solution
str = input("Enter the string: ")
newStr = ""
for ch in str :
    newStr = ch + newStr
print(newStr)
Output
Enter the string: computer studies
seiduts retupmoc

Question 4

Write a program that prompts for a phone number of 10 digits and two dashes, with dashes after the area code and the next three numbers. For example, 017-555-1212 is a legal input. Display if the phone number entered is valid format or not and display if the phone number is valid or not (i.e., contains just the digits and dash at specific places.)

Solution
phNo = input("Enter the phone number: ")
length = len(phNo)
if length == 12 \
    and phNo[3] == "-" \
    and phNo[7] == "-" \
    and phNo[:3].isdigit() \
    and phNo[4:7].isdigit() \
    and phNo[8:].isdigit() :
    print("Valid Phone Number")
else :
    print("Invalid Phone Number")
Output
Enter the phone number: 017-555-1212
Valid Phone Number

=====================================

Enter the phone number: 017-5A5-1212
Invalid Phone Number

Question 5

Write a program that should do the following :

  • prompt the user for a string
  • extract all the digits from the string
  • If there are digits:
    • sum the collected digits together
    • print out the original string, the digits, the sum of the digits
  • If there are no digits:
    • print the original string and a message "has no digits"

Sample

  • given the input : abc123
    prints abc123 has the digits 123 which sum to 6
  • given the input : abcd
    prints abcd has no digits
Solution
str = input("Enter the string: ")
sum = 0
digitStr = ''
for ch in str :
    if ch.isdigit() :
        digitStr += ch
        sum += int(ch)
if not digitStr :
    print(str, "has no digits")
else :
    print(str, "has the digits", digitStr, "which sum to", sum)
Output
Enter the string: abc123
abc123 has the digits 123 which sum to 6

=====================================

Enter the string: KnowledgeBoat
KnowledgeBoat has no digits

Question 6

Write a program that should prompt the user to type some sentence(s) followed by "enter". It should then print the original sentence(s) and the following statistics relating to the sentence(s) :

  • Number of words
  • Number of characters (including white-space and punctuation)
  • Percentage of characters that are alphanumeric

Hints

  • Assume any consecutive sequence of non-blank characters is a word.
Solution
str = input("Enter a few sentences: ")
length = len(str)
spaceCount = 0
alnumCount = 0

for ch in str :
    if ch.isspace() :
        spaceCount += 1
    elif ch.isalnum() :
        alnumCount += 1

alnumPercent = alnumCount / length * 100

print("Original Sentences:")
print(str)

print("Number of words =", (spaceCount + 1))
print("Number of characters =", (length + 1))
print("Alphanumeric Percentage =", alnumPercent)
Output
Enter a few sentences: Python was conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands. Its implementation began in December 1989. Python 3.0 was released on 3 December 2008.
Original Sentences:
Python was conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands. Its implementation began in December 1989. Python 3.0 was released on 3 December 2008.
Number of words = 34
Number of characters = 206
Alphanumeric Percentage = 80.48780487804879

Question 7

Write a Python program as per specifications given below:

  • Repeatedly prompt for a sentence (string) or for 'q' to quit.
  • Upon input of a sentence s, print the string produced from s by converting each lower case letter to upper case and each upper case letter to lower case.
  • All other characters are left unchanged.

For example,
Please enter a sentence, or 'q' to quit : This is the Bomb!
tHIS IS THE bOMB!
Please enter a sentence, or 'q ' to quit : What's up Doc ???
wHAT'S UP dOC ???
Please enter a sentence, or 'q' to quit : q

Solution
while True :
    str = input("Please enter a sentence, or 'q' to quit : ")
    newStr = ""
    if str.lower() == "q" :
        break
    for ch in str :
        if ch.islower() :
            newStr += ch.upper()
        elif ch.isupper() :
            newStr += ch.lower()
        else :
            newStr += ch
    print(newStr)
Output
Please enter a sentence, or 'q' to quit : This is the Bomb!
tHIS IS THE bOMB!
Please enter a sentence, or 'q' to quit : What's up Doc ???
wHAT'S UP dOC ???
Please enter a sentence, or 'q' to quit : q

Question 8

Write a program that does the following :

  • takes two inputs : the first, an integer and the second, a string
  • from the input string extract all the digits, in the order they occurred, from the string.
    • if no digits occur, set the extracted digits to 0
  • add the integer input and the digits extracted from the string together as integers
  • print a string of the form :
    "integer_input + string_digits = sum"

For example :
For inputs 12, 'abc123' → '12 + 123 = 135'
For inputs 20, 'a5b6c7' → '20 + 567 =587'
For inputs 100, 'hi mom' → '100 + 0 = 100'

Solution
num = int(input("Enter an integer: "))
str = input("Enter the string: ")

digitsStr = ''
digitsNum = 0;

for ch in str :
    if ch.isdigit() :
        digitsStr += ch

if digitsStr :
    digitsNum = int(digitsStr)

print(num, "+", digitsNum, "=", (num + digitsNum))
Output
Enter an integer: 12
Enter the string: abc123
12 + 123 = 135

=====================================

Enter an integer: 20
Enter the string: a5b6c7
20 + 567 = 587

=====================================

Enter an integer: 100
Enter the string: hi mom
100 + 0 = 100

Question 9

Write a program that takes two strings from the user and displays the smaller string in single line and the larger string as per this format :

1st letter                  last letter
    2nd letter          2nd last letter
        3rd letter  3rd last letter  

For example,
if the two strings entered are Python and PANDA then the output of the program should be :

PANDA
P          n
  y      o
    t  h
Solution
str1 = input("Enter first string: ")
str2 = input("Enter second string: ")

small = str1
large = str2

if len(str1) > len(str2) :
    large = str1
    small = str2

print(small)

lenLarge = len(large)
for i in range(lenLarge // 2) :
    print(' ' * i, large[i], ' ' * (lenLarge - 2 * i), large[lenLarge - i - 1], sep='')
Output
Enter first string: Python
Enter second string: PANDA
PANDA
P      n
 y    o
  t  h

Question 10

Write a program to convert a given number into equivalent Roman number (store its value as a string). You can use following guidelines to develop solution for it:

  • From the given number, pick successive digits, using %10 and /10 to gather the digits from right to left.
  • The rules for Roman Numerals involve using four pairs of symbols for ones and five, tens and fifties, hundreds and five hundreds. An additional symbol for thousands covers all the relevant bases.
  • When a number is followed by the same or smaller number, it means addition. "II" is two 1's = 2. "VI" is 5 + 1 = 6.
  • When one number is followed by a larger number, it means subtraction. "IX" is 1 before 10 = 9. "IIX isn't allowed, this would be "VIII". For numbers from 1 to 9, the symbols are "I" and "V", and the coding works like this. "I" , "II", "III", "IV", "V", "VI", "VII", "VIII", "IX".
  • The same rules work for numbers from 10 to 90, using "X" and "L". For numbers from 100 to 900, using the symbols "C" and "D". For numbers between 1000 and 4000, using "M".

Here are some examples. 1994 = MCMXCIV, 1956 = MCMLVI, 3888= MMMDCCCLXXXVIII

Solution
n = int(input("Enter the number: "))
num = (1000, 900,  500, 400, 100,  90, 50,  40, 10,  9,   5,  4,   1)
rom = ('M',  'CM', 'D', 'CD','C', 'XC','L','XL','X','IX','V','IV','I')

result = ''

for i in range(len(num)) :
    count = int(n / num[i])
    result += str(rom[i] * count)
    n -= num[i] * count

print(result)
Output
Enter the number: 1994
MCMXCIV

=====================================

Enter the number: 1956
MCMLVI

=====================================

Enter the number: 3888
MMMDCCCLXXXVIII

Question 11

Write a program that asks the user for a string (only single space between words) and returns an estimate of how many words are in the string. (Hint. Count number of spaces)

Solution
str = input("Enter a string: ")
count = 0
for ch in str :
    if ch.isspace() :
        count += 1
print("No of words =", (count + 1))
Output
Enter a string: Python was conceived in the late 1980s by Guido van Rossum at Centrum Wiskunde & Informatica (CWI) in the Netherlands.
No of words = 20

Question 12

Write a program to input a formula with some brackets and checks, and prints out if the formula has the same number of opening and closing parentheses.

Solution
str = input("Enter a formula: ")
count = 0

for ch in str :
    if ch == '(' :
        count += 1
    elif ch == ')' :
        count -= 1

if count == 0 :
    print("Formula has same number of opening and closing parentheses")
else :
    print("Formula has unequal number of opening and closing parentheses")
Output
Enter a formula: s(s-a)(s-b)(s-c)
Formula has same number of opening and closing parentheses

=====================================

Enter a formula: s((s-a)(s-b)(s-c)
Formula has unequal number of opening and closing parentheses

Question 13

Write a program that inputs a line of text and prints out the count of vowels in it.

Solution
str = input("Enter a string: ")
count = 0

for ch in str : 
    lch = ch.lower()
    if lch == 'a' \
       or lch == 'e' \
       or lch == 'i' \
       or lch == 'o' \
       or lch == 'u' :
       count += 1

print("Vowel Count =", count)
Output
Enter a string: Internet of Things
Vowel Count = 5

Question 14

Write a program to input a line of text and print the biggest word (length wise) from it.

Solution
str = input("Enter a string: ")
words = str.split()
longWord = ''

for w in words :
    if len(w) > len(longWord) :
        longWord = w

print("Longest Word =", longWord)
Output
Enter a string: TATA FOOTBALL ACADEMY WILL PLAY AGAINST MOHAN BAGAN
Longest Word = FOOTBALL

Question 15

Write a program to input a line of text and create a new line of text where each word of input line is reversed.

Solution
str = input("Enter a string: ")
words = str.split()
newStr = ""

for w in words :
    rw = ""
    for ch in w :
        rw = ch + rw
    newStr += rw + " "

print(newStr)
Output
Enter a string: Python is Fun
nohtyP si nuF
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