PRIP 2.1 Sumita Arora Solutions | Class 12 Computer Science

Answer:

Note:
a = "blueberry"# in a[left:right] left is included but right is excluded 
# if a[1:4] printed it will include characters from 1 to 3 and not 4


Code:
print(a[2:3]) # at 2 char is 'u' and from 2 to 2 (3 - 1) hence, it will print 'u'  
print(a[2:])  # from 2 to the end of string i.e. from u to end of string
print(a[:3])  # from start of string to 2 (3 - 1)
print(a[:])   # from start of string to end of string
print(a[-1:-3]) # nothing will be printed because -1 > -3  and in a[left:right] left has to be  less than right
print(a[:-1]) # from start of string to -1-1 means 2nd last character 'r'
print(a[1:1]) # as start and end both are same noting will be printed


Output:
1. u
2. ueberry
3. blu
4. blueberry
5.
6. blueberr
7.

Answer:

Note:
In many problems it becomes necessary to process a string through each character. It starts at the beginning, select each character one by one, and continue until the end. This pattern of processing is called a traversal.


Code:
str = input("Enter String ")          # input the string from user
vowels = ['a','e','i','o','u']        # create list of vowels
output_str = ''                       # create empty string
for s in str:                         # traverse over string str
    if s not in vowels:               # check if char 's' is not present in vowels list
        output_str +=s                # if yes append char s to newly created string output_str
print(output_str)                     # print modified string    


Output:
Enter String blueberry
blbrry

Answer:

Code:
str = input("Enter String ")          # input the string from user
vowels = ['a','e','i','o','u']        # create list of vowels
output_str = ''                       # create empty string
for s in str:                         # traverse over string str
    if s in vowels:               # check if char 's' is present in vowels list
        output_str +='({})'.format(s) # if yes append char s to newly created string output_str with 
    else:
        output_str +=s                #else append s without parentheses
print(output_str)                     # print modified string   


output:
Enter String blueberry
bl(u)(e)b(e)rry

Answer:

a) 
myTuple1 = (1,2,3) 
myTuple1.append(4)
print(myTuple1)

Output:
AttributeError: 'tuple' object has no attribute 'append'
tuples are unchangeable
once tuple is created they can't be modified


b)
myTuple2 = (1,2,3)
myTuple3 = (4) 
print(myTuple2 + myTuple3)

Output:
TypeError: can only concatenate tuple (not "int") to tuple
myTuple3 is of type int because tuple consist of only 1 element which is of int type
and concatenation of tuple and int is not possible


c)
myList=[0,3,4,1] 
myList.remove(3)
print(myList)

Output:
[0, 4, 1]
list.remove() takes element to be removed from list as parameter
as 3 passed in as a parameter, 3 is removed from list

Answer:

1. myList = myList + [4]
   Ans:  LEGAL
   Code: myList = [1,2,3]
         myList = myList + [4]
         print(myList) 
   Output: [1, 2, 3, 4]   
    
2. myList.append(4)
   Ans: LEGAL
   Code: myList.append(4)
          print(myList)
   Output: [1, 2, 3, 4, 4]

3. del myList[0]
    Ans: LEGAL
    Code: del myList[0]
            print(myList)
    Output: [2, 3, 4, 4]
    
4. myTuple = myTuple + (4)
    Ans: ERROR
    Code: myTuple = (1,2,3)
    Output: TypeError: can only concatenate tuple (not "int") to tuple

5. myTuple.append(4)
    Ans: ERROR    
    Reason: AttributeError: 'tuple' object has no attribute 'append'
          #A tuple is a collection which is ordered and unchangeable.

6. del myTuple[0]
    Ans: ERROR    
    Reason: TypeError: 'tuple' object doesn't support item deletion

7. myString = myString + "4"
    Ans: LEGAL    
    Code:myString = 'ComputerTutor'
         myString = myString + "4"
         print(myString)
    output: #ComputerTutor4

8. myString.append(4)
   Ans: ERROR
   Reason: #AttributeError: 'str' object has no attribute 'append'

9. del myString[0]
   Ans: ERROR
   Reason: #TypeError: 'str' object doesn't support item deletion

Answer:

Output:
Final value of a = [5, 0]


Explanation: 
a = [1, 2, 3] 
a[2] = 0   # update a[2] to 0 i.e. 3 will be replaced by 0
print(a)   # [1, 2, 0]  

a[a[2]]= 5 # update a[a[2]] = a[0] = 5  i.e. 1 will be replaced by 5
print(a)   #[5, 2, 0]

a[1:2] = [] # from 1 to 1 (2 - 1) i.e. a[1] = [] 
print(a)   # [5, 0]

Answer:

Code:
input_str = input("Enter list elements space separated : ") # inputs the list as string
input_list = list(map(int ,input_str.split()))              # split string and convert it into a list of integers
del input_list[0]                                           # delete element at index 0
print(input_list)                                           # print modified list


Output:
Enter list elements space separated : 1 2 3 
[2, 3]

Answer:

Code:
a = [[[ 1,2,3,4,5],[6,7,8]],9] #initial 
a[-1] = 200 # last element changed to 200
b = a[:]    # all elements of a copied to b
b[0][0][3] = 17 
# 0th element of b = [[ 1,2,3,4,5],[6,7,8]]
# 0th element of [[ 1,2,3,4,5],[6,7,8]] = [ 1,2,3,4,5,]
# 3rd element of [ 1,2,3,4,5] = 4 
# 4 will be replaced by 17

print(a) 
print(b)

# making copy of a list simply by typing b = a leads to problem
# b will only be a reference to a, and changes made in b will automatically also be made in a.


Output:
[[[1, 2, 3, 17, 5], [6, 7, 8]], 200]
[[[1, 2, 3, 17, 5], [6, 7, 8]], 200]

Answer:

Code:
tuple1 = (1, 2, 3)
tuple2 = (4, 5, 6)
tuple3 = tuple1 +  tuple2 # concatenate  tuple1 & tuple2   
print(tuple3)


Output:
(1, 2, 3, 4, 5, 6)

Answer:

this problem can be easily solved by using inbuilt function in list called sort()

Code:
a = [3, 4, 1, 5, 8, 2]
a.sort()
print("Output using inbuilt function : {}".format(a))

Output:
Output using inbuilt function : [1, 2, 3, 4, 5, 8]

To understand logic of sorting two more methods are given:

Method 1:
a = [3, 4, 1, 5, 8, 2]
n = len(a)
for i in range(n):         #traverse through array
    for j in range(n):   
        if(a[i]<a[j]):     # check if a[i] < a[j] if true swap a[i] a[j]
            temp = a[i]
            a[i] = a[j]
            a[j] = temp
print("Output of simple approach : {}".format(a))

Output:
Output of simple approach : [1, 2, 3, 4, 5, 8]


Method 2:
# bubble sort   
# each element is comapired with remaining elements and 
#if current element is greater than its next element they get swapped
# with each iteration largest element in remaining array will shifted to last
a = [3, 4, 1, 5, 8, 2]
n = len(a)

for i in range(n-1): 
    for j in range(0, n-i-1):  #in each iteration range is reduced by 1
            # Swap if a[j] (current element) is greater than a[j+1] (next element)  
        if a[j] > a[j+1] : 
            temp = a[j]
            a[j] = a[j+1]
            a[j+1] = temp
print("Output of bubble sort approach : {}".format(a))

Output:
Output of bubble sort approach : [1, 2, 3, 4, 5, 8]

Answer:

if we try sorting tuple same as list we will get error like 
TypeError: 'tuple' object does not support item assignment

Reason: tuples are immutable i.e. they can't be changed

to sort tuple we can follow two methods:
1. covert tuple to list sort it and again convert it to tuple
2. use built in sorted() function to sort tuple directly
    sorted() will return sorted tuple 


Method 1:
a_tuple = (3, 4, 1, 5, 8, 2)
a_list = list(a_tuple)
n = len(a_list)
for i in range(n):         #traverse through array
    for j in range(n):   
        if(a_list[i]<a_list[j]):     # check if a[i] < a[j] if true swap a[i] a[j]
            temp = a_list[i]
            a_list[i] = a_list[j]
            a_list[j] = temp
a_tuple = tuple(a_list)
print("Output of tuple to list approach : {}".format(a_tuple))

Output:
Output of tuple to list approach : (1, 2, 3, 4, 5, 8)


Method 2:
a_tuple = (3, 4, 1, 5, 8, 2)
output_tuple = sorted(a_tuple)
print("Output of sorted method approach : {}".format(tuple(output_tuple)))

Output:
Output of sorted method approach : (1, 2, 3, 4, 5, 8)

Answer:

Since the question is confusing and there is no fix expected output we are providing two different approaches which gives different output

Method 1:
a = [[1,2,3],
     [4,5,6],
     [7,8,9]]

row = len(a)   # calculate number of rows
col = len(a[0])# calculate number of cols
n = row*col//2 # total number of swaps required
count = 0

for r in range(row): # iterate rows
    for c in range(col): #iterate columns

        if count<=n:     # if number of swaps less than n
            temp = a[r][c] # then swap
            a[r][c] = a[row-1-r][col-1-c]
            a[row-1-r][col-1-c] = temp
            count+=1     # increment the swap counter

# Code for printing 2D array    
for i in  range(row) :  
    for j in range(col) : 
        print(a[i][j],end= ' '); 
    print(); 


Output:  
9 8 7 
6 5 4 
3 2 1

Method 2:
a = [[1,2,3],
     [4,5,6],
     [7,8,9]]
row = len(a)
col = len(a[0])

for i in range(row) : # traverse through each row
    left = 0; # Initialize start
    right = col - 1; # Initialize end

    while (left < right) :   # Till start < end, swap the element at start and end  
        # Swap the elements 
        temp = a[i][left]
        a[i][left] = a[i][right] 
        a[i][right] = temp
        left += 1; #Increment start
        right -= 1;   #decrement end

# Code for printing 2D array
for i in  range(row) : 
    for j in range(col) : 
        print(a[i][j],end= ' '); 
    print();


Output: 
 3 2 1 
 6 5 4 
 9 8 7