NCERT Solutions Class 11 Computer Science (Python) Chapter-13 (Lists, Dictionaries and Tuples)

NCERT Solutions Class 11 Indian Economic Development from class 11th Students will get the answers of Chapter-13 (Lists, Dictionaries and Tuples) This chapter will help you to learn the basics and you should expect at least one question in your exam from this chapter.

We have given the answers of all the questions of NCERT Board Computer Science (Python) Textbook in very easy language, which will be very easy for the students to understand and remember so that you can pass with good marks in your examination.

NCERT Question-Answer

Class 11 Computer Science (Python)

Chapter-13 (Lists, Dictionaries and Tuples)

Questions and answers given in practice

Chapter-13 (Lists, Dictionaries and Tuples)

Topic – 1
Lists

Very Short Answer Type Questions (1 marks each)

Question 1:
How many types of built-in types of sequences in Python.
Answer:
Python has six built-in types of sequences.

Question 2:
Write the output of the given Python code.

# !/user/bin/python
list1 = [‘physics’, ‘chemistry’, 1997, 2000];
list2 = [1,2,3,4,5,6, 7];
print “list1[0]”, list1[0]

Answer:

list1[0]: physics

Question 3:
Write the output of the given Python code.

# !/user/bin/python
listl = [‘physics’, ‘chemistry’, 1997,2000];
list2 = [1,2, 3,4,5, 6, 7];
print “list2[l:5[ :”, list2[l:5]

Answer:

list2[1:5[: [2,3,4,5]

Question 4:
How can we remove list element ?
Answer:
To remove a list element, you can use either the del statement or the remove]) method

Question 5:
Why we use cmp(listl, list2) in Python?
Answer:
It compares elements of both lists.

Question 6:
What is the use of len(list)) in Python?
Answer:
It gives the total length of the list.

Question 7:
Describe max(list) method.
Answer:
It returns item from the list with max value.

Question 8:
Describe min(list) method.
Answer:
It returns item from the list with min value.

Question 9:
What is the use of list(seq) in Python ?
Answer:
It converts a tuple into list.

Question 10:
What do you mean by list.append(obj)
Answer:
Appends object obj to list

Question 11:
What do you mean by list.count(obj)
Answer:
Returns count how many times obj occurs in list

Question 12:
Explain list.extend(seq)
Answer:
Appends the contents of seq to list.

Question 13:
Is list.reverse() method return a value?
Answer:
This method does not return any value but reverse the given object from the list

Question 14:
Which method is used to sort objects of list.
Answer:
sort ()

Question 15:
Which function is used to reverse objects of list in place.
Answer:
list.reverse ()

Question 16:
Which function is use for removing object obj from list.
Answer:
list.remove(obj)

Question 17:
Which function is use for returning the lowest index in list that obj appears.
Answer:
List index (obj).

Short Answer Type Questions (2 marks each)

Question 1:
Define list in Python.
Answer:
The list is a most versatile datatype available in Python which can be written as a list of comma- separated values (items) between square brackets. Good thing about a list is that items in a list need not all have the same type. Creating a list is as simple as putting different comma-separated values between square brackets.
For example :
list1 = [‘physics’, ‘chemistry’, 1997,2000];
list2 = [1,2, 3,4, 5];
list3 = ’[‘a”, “b”, “c”, “d”];

Question 2:
Give an example to access values in lists.
Answer:
To access value in lists, use the square brackets for slicking along with the index or indices to obtain value available at that index. Following is a simple example :

# !/user/bin/python
list1 = [‘physics’, ‘chemistry’, 1997, 2000];
list2 = [1, 2, 3, 4, 5, 6, 7];
print “list1 [0]:”,
list1 [0] print “list2[1 :5]:”, list2[1:5]

When the above code is executed, it produces the following result:

list1 [0]: physics
list2[1:5] : [2, 3, 4, 5]

Question 3:
Give an example to update single or multiple elements of lists
Answer:
You can update single or multiple elements of lists by giving the slice on the left-hand side of the assignment operator, and you can add elements in a list with the append( ) method. Following is a simple example:

# !/user/bin/python
listl = [‘physics’, ‘chemistry’, 1997, 2000];
print “Value available at index 2 :”
print list[2];
list[2] = 2001;
print “New value available at index 2 :”
print list [2];
Note: append)) method is discussed in subsequent section.

When the above code is executed, it produces the following result:

Value available at index 2 :
1997
New value available at index 2 :
2001

Question 4:
Give an example to remove list element.
Answer:
To remove a list element, you can use either I the del statement if you know exactly which ‘ element(s) you are deleting or the remove I ( ) method if you do not know. Following is a simple example:

# !/user/bin/python
list1 = [‘physics’, ‘chemistry’, 1997, 2000];
print list1;
del list1 [2];
print “After deleting value at index 2 :”
print list1;

When the above code is executed, it produces the following result:

[‘physics’, ‘chemistry’, 1997, 2000];
After deleting value at index 2;
[‘physics’, ‘chemistry’, 2000]

Question 5:
Describe list() with its syntax.
Answer:
The method list() takes sequence types and converts them to lists. It is used to convert a given tuple into list.
Syntax
Following is the syntax for list() method :
list (seq)

Question 6:
Write the output of the given Python code :

#!/user/bin/python
list1, list2 = [123, ‘xyz’], [456, ‘abc’]
print cmpt(list1, list2);
print cmp(list2, list1);
list3 = list2 + [786];
print cmp(list2, list3)

Answer:

This will produce the following result:
-1
1
-1

Question 7:
Write the output of the given Python code :

#!/user/bin/python
aList = [123, ‘xyz’, ‘zara’, ‘abc’, 123];
bList = [2009, ‘manni’];
aList.extend (bList)
print “Extended List :”, aList;

Answer:

This will produce the following result:
Extended List : [123, ‘xyz’, ‘zara’, ‘abc’, 123, 2009, ‘manni’]

Question 8:
Write the output of the given python code :

# ! ‘user/bin’pvthon
aList1 = [123, ‘xvz’, zara’, abc’];
print “Index for xyz : ” aList. index) ‘xyz’);
print “Index for zara :”, aList. index(‘zara’);

Answer:

This will produce the following result:
Index for xyz : 1 Index for xxx : 2

Question 9:
Write the output of the given python code :
# !/user/bin/python
aList = [123, ‘xyz’, ‘zara’, ‘abc’];
aList.insert (3,2009) print “Final List:”, aList
Answer:
Output:
Final List: [123, ‘xyz’, ‘zara’, 2009, ‘abc’]

Question 10:
Write the output of the given python code :

#!/user/bin/python
aList1 = [123, ‘xyz’, ‘zara’, ‘abc’];
aList.insert (3,2009) print “Final Lista List

Answer:

Output:
Final List: [123, ‘xyz’, ’zara1, 2009,’abc1’]

Question 11:
Write the output of the given python code :

# !/user/bin/python
aList1 = [123, ‘xyz’, ‘zara’, ‘abc’];
print “A List:”, aList.pop()
print “B List:”, aList.pop(2)

Answer:

Output:
A List: abc B List: zara

Question 12:
Write the output of the following code [CBSE Text Book]

A = [2, 4, 6, 8,10]
L = len (A)
S = o
for I in range (1, L, 2):
S + = A[I]
print “Sum=”, S

Answer:

Sum = 12
Justification:
A[1] = 4 step size = 2
A[3] = 8
S = 4 + 8 = 12

Question 13:
How are lists different from strings when both are sequences ?
Answer:
The lists and strings are different in following ways :

(a) The lists are mutable sequences while strings are immutable.
(b) Strings store single type of elements, all characters while lists can store elements belonging to different types.
(c) In consecutive locations, strings store the individual characters while list stores the references of its elements.

Question 14:
Write a program to calculate and display the sum of all the odd numbers in the list.
Answer:

pos = 0
sum = 0
while pos < len (L):
if L[pos] %2 = = 1 :
sum = sum + L [pos]
pos = pos + 1
print sum

Question 15:
Define a function overlapping ( ) that takes two lists and returns True if they have at least one member in common, False otherwise.
Answer:

def overlapping (a, b):
11 = len (a)
12 = len (b)
for i in range (11):
for j in range (12):
if a[i] == b[j] :
return True
else
return False

Question 16:
Write a program to find all duplicates in a list. [CBSE Text Book]
Answer:

a =[1,2,3,2,1,5,6,5,5,5]
d={ }
for elem in a:
if elem in
d: d[elem] + = 1
else:
d[elem] = 1
print elem
print [x for x, y in d.items() if y > 1],
print “have duplicates”
print d

Output screenshot:

[1,2,5] have duplicates
{1:2,2: 2,3:1,5:4, 6: 1}

Long Answer Type Questions (4 marks each)

Question 1:
What is string in Python and how can we access values in list.
Answer:
The most basic data structure in Python is the sequence. Each element of a sequence is assigned a number – its position or index. The first index is zero, the second index is one, and so forth. Python has six built -in types of sequences, but the most common ones are lists and tuples.
There are certain things you can do with all sequence types. These operations include indexing, slicing, adding, multiplying, and checking for membership. In addition, Python has built-in functions for finding the length of a sequence and for finding its largest and smallest elements.
Python Lists:
The list is a most versatile datatype available in Python which can be written as a list of comma- seprated values (items) between brackets. Good thing about a list is that items in a list need not all have the same type.
Creating a list is as simple as putting different comma-separated values between square brackets. For example:

list1 = [‘physics’, ‘chemistry’, 1997,2000];
list2 = [1, 2, 3,4,5];
list3 = [“a”, “b”, ”c”, “d”];
Like string indices, list indices start at 0, and lists can be sliced, concatenated and so on.

Accessing Values in Lists :

To access values in lists, use the square brackets for slicing along with the index or indices to obtain value available at that index. Following is a simple example :

# !/user/bin/python
list = [‘physics’, ‘chemistry’, 1997,2000];
list2 = [1,2, 3,4,5,6, 7];
print “list1 [0]:”, list1 [0]
print “list2[1:5]:”, list2[1:5]
list 2[1:5]: [2, 3, 4, 5]

Question 2:
How can we update and delete list in python.
Answer:

Updating Lists:
You can update single or multiple elements of lists by giving the slice on the left-hand side of the assignment operator, and you can add to elements in a list with the append() method. Following is a simple example:

# !/user/bin/python
list = [‘physics’, ‘chemistry’, 1997, 2000];
print “Value available at index 2 :”
print list[2];
list [2] = 2001;
print “New value available at index 2 :”
print list [2];

When the above code is executed it produces the following result:

Value available at index 2 :
1997
New value available at index 2 :
2001
Delete List Elements:
To remove a list element, you can use either the del statement if you know exactly which element(s) you are deleting of the remove() method if you do not know.
Following is a simple example :

# !/user/bin/python
list1 = [‘physics’, ‘chemistry’, 1997, 2000];
print list1; del list1 [2];
print “After deleting value at index 2:”
print list1;

When the above code is executed, it produces the following result:

[‘physics’, ‘chemistry’, 1997, 2001]
After deleting value at index 2 :
[‘physics’, ‘chemistry’, 2000]

Question 3:
Write a program to input any two matrices and print sum of matrices.
Answer:

import random
m1 = input (“Enter total number of rows in the first matrix”)
n1 = input (“Enter total number of columns in the first matrix”)
a = [[random.random() for row in range(m1) for col in range (n1)]
for i in range (m1)
for j in range (n1):
a[i][j] = input()
m2 = input (“Enter total number of rows in the second matrix”)
n2 = input (“Enter total number of columns in the second matrix”)
b = [[random.random () for row in range (m2)] for col in range (n2)]
for i in range (m2):
for j in rnage (n2):
b [i][j] = input ()
c = [[random.random () for row in range (ml)] for col in range (n1)]
if ((m1 = m2) and (n1 = = b)):
print “Output is”
for i in range (m1):
for j in range (n1)]
c[i][j] = a[i][j] + b[i][j]
print c[i][j], ‘it’,
print
else :
print “Matrix addition is not possible”

Question 4:
Write a program to input any two matrices and print product of matrices.
Answer:

import random
m1 = input (“Enter number of rows in first matrix”)
n1 = input (“Enter number of columns in first matrix”)
a = [[random.random () for row in range (m1)] for col in range (n1)]
for i in range (m1):
for j in range (n1):
a[i][j] = input ()
m2 = input (“Enter the number of rows in the second matrix”)
n2 = input (“Enter the number of columns in the second matrix”)
b = [[random.random () for row in range (m2)] for cal in range (n2)]
for i in range (m2):
for j in range (n2):
b[i][j] = input ()
c = [[random.random () for row in range (ml)] for col in range (n2)]
if (n1 = = m2):
for i in range (m1):
for j in range (n2):
c[i][j] = 0 for kin range (n1):
c[i][j] + = a[i][k]*b[k][j]
print c[i][j], ‘\t’,
print
else:
print “Multiplication is not possible”

Question 5:
Write a program to input any matrix and print both diagonal values of the matrix.
Answer:

Import random
m = input (“Enter the number of rows”)
n = input (“Enter the number of columns”)
a = [[random.random () for row in range (m)] for cal in mange (n)]
if i in range (m):
for j in range (n):
a[i][j] = input ()
print “First diagonal”
for i in range (m):
print a[i][j], ‘\t’
k = m – 1
print “second diagonal”
for j in range (m):
print a[j][k], ‘\t’
k- = 1
else:
print “Diagonal values are not possible”

Question 6:
Write a program to input n x m matrix and find the sum of all numbers.
Answer:

def summat (a, m, n):
s = 0
for i in range (m):
for j in range (n):
s + = a[i][j]
return s

Question 7:
Write a program to perform various list operations after displaying menu.
Answer:

ch = 0
list = []
while true :
print “List Menu”
print “1. Adding”
print “2.Modify”
print “3.Delete”
print “4.Sort list”
print “5.Display list”
print “6.Exit”
ch = int (raw_input (“Enter your choice :”)) if ch = = 1 :
print “1.Add element”
print “2.Add a List”
ch1 = int (raw_input
(“Enter choice 1 or 2:”))
if chi = = 1:
item = int
(raw_input (“Enter element:”))
pos = int (raw_input
(“Enter position to add : “))
list.insert (pos, item)
elif chi = = 2 :
list2 = eval (raw_input (“Enter list:”))
list.extend (lst2)
else:
print “Valid choices are 1 or 2”
print “Successfully added” elif ch = = 2 :
pos = int (raw_input
(“Enter position :”))
intem = int (raw_input
(“Enter new value :”))
old = list[pos]
list[.pos] = item
print old, ‘modified with vlaue”, item elif ch = = 3:
print “1.Delete element by position”
print “2.Delete element by value”
ch1 = int (raw_input (“Enter you choice 1 or 2’))
if chi = = 1:
pos = int (raw_input (“Enter position :”))
item = list.pop (pos)
print item, “deleted”
elif ch1 = = 2:
item = int (raw_input (“Enter element:”))
pos = list.remove (item)
print “Succcessfully delted”
else :
print “Valid choices are 1 or 2”
elif ch = = 4 :
print “l.Ascending”
print “2.Descending”
chi = int (raw input (“Enter choice 1 or 2”))
if chi = = 1:
list. sot () elif ch1 = = 2:
list.sort (reverse = True)
else :

print “Valid choices are 1 or 2”

elif ch = = 5:
print list elif ch = = 6:
break
else :
print “valid choice 1 to 6”

Question 8:
Write a program to pass any list and to arrange all numbers in descending order.
Answer:

def arrange (1, n)
for i in range (n – 1):
for j in range (n – i – 1):
if l[j] > l[j +1] :
temp = l[j]
l[j] = l[j+l]
l[j+l] = temp

Question 9:
Write the output for the following codes. [CBSE Text Book]

A= (10:1000,20:2000,30:3000,40:4000, 50:5000}
print A.items()
print A.keys()
print A.values()

Answer:

[(40, 4000), (10, 1000), (20, 2000), (50, 5000), (30, 3000)]
[40,10, 20, 50, 30]
[4000,1000, 2000,5000,3000]

Topic – 2
Tuples

Very Short Answer type Questions [1 mark each]

Question 1:
What is a tuple ?
Answer:
Tuple is a sequence of immutable Python objects

Question 2:
Can we remove individual tuple elements ?
Answer:
No, we cannot remove individual tuple elements.

Question 3:
Which function is use for comparing elements of both tuples.
Answer:
cmp(tuplel, tuple2)

Question 4:
Which function gives the total length of the tuple.
Answer:
len(tuple)

Question 5:
Which function returns item from the tuple with max value.
Answer:
max(tuple)

Short Answer type Questions [2 mark each]

Question 1:
What is tuple ?
Answer:
Tuple is a sequence of immutable Python objects. Tuples are sequences, just like lists.
The only difference is that tuples can’t be changed i.e.,tuples are immutable and tuples use parentheses and lists use square brackets. Creating a tuple is as simple as putt ing different comma- separated values and optionally you can put these comma-separated values between parentheses also.
For example :
tup1 = (‘physics’, ‘chemistry’, 1997, 2000);
tup2 = (1,2, 3,4, 5);
tup3 = “a”, “b”, “c”, “d”;

Question 2:
Write the output of the given python code :
#!/user/bin/python
tup1 = (12, 34.56);
tup2 = (‘abc’, ‘xyz’);
#Following action is not valid for tuples
#tup1 [0] = 100;
#So let’s create a new tuple as follows
tup3 = tup1 + tup2;
print tup3;
Answer:
Output :
(12,34.56, ’abc’, ‘xyz’)

Question 3:
Write the output of the given python code :
# !/user/bin/python
tuple1, tuple2 = (123, ‘xyz’), (456, ‘abc’)
print cmp (tuple1, tuple2) ;
print cmp (tuple2, tuple1) ;
tuple3 = tuple2 + (786,);
print cmp (tuple2, tuple3)
Answer:
Output :
-1
1
-1

Question 4:
Write the output of the given python code :
#!/user/bin/python
tuple1, tuple2 = (123, ‘xyz’, ‘zara’, ‘abc’), (456, 700, 200)
print “min value element : “, min (tuple1);
print “min value element : “, min (tuple2);
Answer:
Output :
min value element : 123
min value element : 200

Long Answer type Questions [4 mark each]

Question 1:
What is tuple in Python and how can we access values in tuples ?
Answer:
Tuple is a sequence of immutable Python object. Tuples are sequences, just like lists. The only difference is that tuples can’t be changed i.e.,tuples are immutable and tuples use parentheses and lists use square brackets.
Creating a tuple is as simple as putting different comma-separated values and optionally you can put these comma -separated values between parentheses also.
For example :
tup1 = (‘physics’, ‘chemistry1,1997,2000) ;
tup2 = (1, 2, 3, 4, 5);
tup3 = “a”, “b”, “c”, “d”;
The empty tuple is written as two parentheses containing nothing :
tup1 = ( ) ;
To write a tuple containing a single value you have to include a comma, even though there is only one
tup1 = (50,);
Like string indices, tuple indices start at 0, and tuples can be sliced, concatenated and so on. Accessing Values in Tuples :
To access value in tuple, use the square brackets for slicing along with the index or indices to obtain value available at that index.
Following is a simple example :
# !/user/bin/python
tup1 = (‘physics’, ‘chemistry’, 1997,2000);
tup2 = (1, 2, 3,4,5,6, 7);
print “tup1[0]”, tup1[0]
print “tup2[1:5]:”, tup2[1:5]
When the above code is executed, it produces the following result :
tup1[0] : physics
tup2[1:5]: [2, 3,4,5]

Question 2:
How we update and delete tuples ?
Answer:
Updating Tuples :
Tuples are immutable which means you cannot update them or change values of tuple elements. But we are able to take portions of an existing tuples to create a new tuples as follows. Following is a simple example :
#!/user/bin/python
tup1 =(12,34.56);
tup2 = (‘abc’, ‘xyz’);
#Following action is not valid for tuples
#tup1[0] = 100;
#So lets create a new tuple as follows :
tup3 = tup1 + tup2;
print tup3;
When the above code is executed, it produces the following result :
(12,34.56, ‘abc’, ‘xyz’)
Delete Tuple Elements :
Removing individual tuple elements is not possible. There is, of course, nothing wrong with putting together another tuple with the undesired elements discarded.
To explicity remove an entire tuple, just use the del statement. Following is a simple example :
#!/user/bin/python
tup = (‘physics’, ‘chemistry’, 1997,2000);
print tup;
del tup;
print “After deleting tup:”
print tup;
This will produce following result. Note an exception raised, there is because after del tup tuple does not exist any more :
(‘physics’, ‘chemistry’, 1997,2000)
After deleting tup :
Traceback (most recent call last) :
Fill “test.py”, line 9, in < modulo>
print tup;
Name Error : name ‘tup’ is not defined

Question 3:
Explain cmp(tuplel, tuple2) with example.
Answer:
cmp(tuple1, tuple2)
Despription :
The method cmp( ) compares elements of two tuples.
Syntax :
Following is the syntax for cmp( ) method :
cmp (tuplel, tuple2)
Parameters :

tuple 1 – This is the first tuple to be compared
tuple 2 – This is the second tuple to be compared
Return Value :
If elements are of the same type, perform the compare and return the result. If elements are different types, check to see if they are numbers.
If numbers, perform numeric conversion if necessary and compare.
If either element is a number, then the other element is “larger” (numbers are “smallest”).
Otherwise, types are sorted alphabetically by name.

If we reached the end of one of the tuples, the longer tuple is “larger”. If we exhaust both tuples and share the same data, the result is a tie, meaning that 0 is returned.
Example :
The following example shows the usage of cmp( ) method
#!/user/bin/python
tuple1, tuple2 = (123, ‘xyz’), (456, ‘abc’)
print cmp(tuple1, tuple2);
print cmp(tuple1, tuple1);
tuple3 = tuple2 + (786,);
print cmp (tuple2, tuple3)
Let us compile and run the above program, this will produce the following result :
-1
1
-1

Question 4:
Explain tuple(seq) function of the python also give example.
Answer:
tuple(seq)
Description :
The method tuple( ) is used to convert list into a tuple.
Syntax :
Following is the syntax for tuple( ) method :
tuple (seq)
Parameters :
• seq – This is a list to be converted into tuple. Return Value :
This method returns the tuple.
Example :
The following example shows the usage of tupe( ) method.
# !/user/bin/python
aList = [123, ‘xyz’, ‘zara’, ‘abc’];
aTuple = tuple (aList)
print “Tuple elements :”,aTuple
Let us compile and run the above program, this will produce the followin’, result :
Tuple elements : (123, ‘xyz’, ‘zara’, ‘abc’)

Question 5:
Write a program to input ‘n’ numbers and store it in tuple.
Answer:
t = tuple ( )
n = input (“Enter any number”)
print “Enter all numbers one after other”
for i in range (n) :
a = input (“Enter number”)
t = t+(a, )
print “Output is”
print t

Question 6:
Write a program to input any two tuples and interchange the tupel values.
Answer:
t1 = tuple( )
n = input(“Total number of values m first tuple”) for i in range (n):
a = input(“Enter elements”)
t2 = t2 + (a, )
print “First tuple”
print t1
print “Second tuple”
print t2
t1, t2 = t2, t1
print “After swapping”
print “First tuple”
print t1
print “Second tuple”
print t2

Question 7:
Write a program to input ‘n’ numbers and separate the tuple in the following manner.
Example
T=(10,20,30,40,50,60)
Tl=(10,30,50)
T2=(20,40,60)
Answer:
t=tuple( )
n=input(” Enter number of values:”)
for i in range(n):
a=input(“enter elements”)
t=t+(a,)
t1=t2=tuple( )
for i in t:
if i%2 == 0:
t2= t2 + (i,)
else:
tl=tl+(i,)
print “First Tuple”
print t1
print “Second Tuple”
print t2
Output:
Enter number of values: 10
enter elements 1
enter elements 9
enter elements 8
enter elements 5
enter elements 2
enter elements 3
enter elements 6
enter elements 4
enter elements 7
enter elements 10
First Tuple (1, 9, 5, 3, 7)
Second Tuple (8,2,6,4,10)

Question 8:
Write a program to input ‘n’ employees’ salary and find minimum & maximum salary among ‘n’ employees.
Answer:
t=tuple( )
n=input(“Enter total number of employees”)
for i in range(n):
a=input(“enter salary of employee:”)
t=t+(a,)
print “maximum salary=”,max(t)
print “minimum salary=”,min(t)
Output :
Enter total number of employees 3
enter salary of employee: 7800
enter salary of employee: 8934
enter salary of employee:
6544 maximum salary = 8934
minimum salary = 6544

Topic – 3
Dictionaries

Short Answer type Questions [2 mark each]

Question 1:
How are dictionaries different from lists ?
Answer:
The dictionary is similar to lists in the sense that it is also a collection of data-items just like lists but it is different form lists in the sense that lists are sequential collections and dictionaries are non-sequential collections. In lists, where there is an order associated with the data items because they act as storage units for other objects or variables created. Dictionaries are different from lists and tuples because the group of objects they hold are not in any particular order, but rather each object has its own unique name, commonly known as a key.

Question 2:
When are dictionaries more useful than lists ?
Answer:
Dictionaries can be much more useful than lists. For example : suppose we wanted to store all our friend’s cell phone numbers. We could create a list of pairs (phone number, name), but once this list becomes long enough searching this list for a specific phone number will get time consuming. Better would be if we could index the list by our friend’s name. This is precisely what a dictionary does.

Question 3:
Write a program to print the worker’s informations (Name age, salary) in records format.
Answer:
Employees = {‘Rohan’ : {‘age’ : 20, ‘salary’ : 10000}, ‘Mohan’ : {‘age’ : 30, ‘salary’ : 15000}}
for key in Employees :
print “Employee”, key + ‘:’
print ‘Age :’ + str (Employees [key] [‘age’]
print ‘Salary :’ + str (Employees [key] [‘salary’])

Question 4:
What is a key-value pair with reference to Python dictionary ?
Answer:
A dictionary is a mapping between a set of indices (which are called keys) and a set of values. Each key maps a value. The association of a key and a value is called a key-value pair.

Question 5:
What are the characteristics of Python Dictionaries ?
Answer:
The 3 main characteristics of a dictionary are :

Dictionaries are Unordered : The dictionary elements (key-value pairs) are not in ordered form.
Dictionary Keys are Case Sensitive : The same key name but with different case are treated as different keys in Python dictionaries.
No duplicate key is allowed : When duplicate keys encountered during assignment, the last assignment wins.
Keys must be immutable : We can use strings, numbers or tuples as dictionary keys but something like [‘key’] is not allowed.

Long Answer type Questions [4 mark each]

Question 1:
Explain cmp(dict1, dict2) with example.
Answer:
Description
The method cmp( ) compares two dictionaries
based on key and values.
Syntax
Following is the syntax for cmp( ) method :
cmp(dict1, dict2)
Parameters
• dict1 – This is the first dictionary to be compared with dict2.
• dict2 – This is the second dictionary to be compared with dict1.
Return value :
This method returns 10 if both dictionaries are equal, – 1 if dictl < dict2 and 1 if dictl > dict2.
Example :
The following example shows the usage of comp( ) method.
# !/user/bin/python
dict1 = {‘Name’ : ‘Zara’, ‘Age’ : 7};
dict2 = {‘Name1 : ‘Mahnaz’, ‘Age’ : 27};
dict3 = {‘Name’ : ‘Abid’, ‘Age’ : 27);
dict4 = {‘Name’ : ‘Zara’, ‘Age’ : 7};
print “Return Value : %d”, % cmp (dict1, dict2)
print “Return Value : %d”, % cmp (dict2, dict3)
print “Return Value : %d”, % cmp (dictl, dict4)
Let us compile and run the above program, this will produce the following result :
Return Value : – 1 .
Return Value : 1
Return Value : 0

Question 2:
Explain str(dict) with example.
Answer:
Description
The method str( ) produces a printable string representation of a dictionary.
Syntax
Following is the syntax for str( ) method :
str(dict)
Parameters
• diet – This is the dictionary.
Return Value
This method returns string representation.
Example :
The following examples shows the usage of str() method.
# !/user/bin/python
diet = {‘Name’ :’Zara’, ‘Age’ : 7);
print “Equivalent String : %s” %str (dict)
Let us compile and run the above program, this will produce the following result :
Equivalent String : {‘Age’ : 7, ‘Name’ : ‘Zara’}

Question 3:
Describe dict.fromkeys( ) with example.
Answer:
dict.fromkeys( )
The method fromkeys( ) creates a new dictionary with keys from seq and values set to value.
Syntax
Following is the syntax for fromkeys( ) method :
dict.fromkeys{seq[,value])}
Parameters :
• seq – This is the list of values which would be used be used for dictionary keys preparation.
• value – This is optional, if provided then value would be set to this value.
Return Value
This method returns the list.
Example :
The following example shows the usage of fromkeys( ) method.
#!/user/bin/python
seq = {‘name’, ‘age’, ’sex’)
diet = dict.from keys(seq)
print “New Dictionary : %s” % str(dict)
dict = dict.from keys(seq, 10)
print “New Dictionary : %s” % str(dict)
Let us compile and run the above program, this will produce the following result :
New Dictionary : {‘age’ : None, ‘name’ : None, ‘sex’: None}
New Dictionary : {‘age’ : 10, ‘name’ : 10, ‘sex’ : 10}

Question 4:
Write a program to input total number of sections and class teacher’s name in 11th class and display all information on the output screen.
Answer:
class xi = diet ( )
n = input (“Enter total number of section in xi class”)
i = 1
while i < = n :
a = raw_input (“enter section”)
b = raw input (“enter class teacher name”)
classxi[a] = b
i = i + 1
print “Class”, “\t”, “Section”,
\t„, “Teacher Name”
for i in classxi :
print “XI”, “\t”, i, “\t”, class xi[i]

Question 5:
Write a Python program to input ‘n’ names and phone numbers to store it in a dictionary and to input any name and to print the phone number of the particular name.
Answer:
phonebook = dict( )
n = input (“Enter total number of friends”)
i = 1
while i<=n :
a = raw_input (“Enter name”)
b = raw_input (“Enter phone number”)
phonebook [a] = b
i = i + 1
name = raw_input (“Enter name”)
f = 0
l = phonebook.keys( )
for i in l :
if (comp (i, name) = = 0) :
print “Phone number =”, phonebook[i]
f = 1
if (f = = 0):
print “Given name not exist”

Question 6:
Write a Python program to input ‘n’names and phone numbers to store it in a dictionary and to search and print the phone number of that particular name.
Answer:
phonebook=dict( )
n=input(” Enter total number of friends to create a telephone book”)
i=l
while i<=n:
a=raw_input(“enter name”)
b=raw_input(“enter phone number”)
phonebook[a]=b
i=i+l
name=raw_input(“enter friend’s name to search for”)
f=0
l=phonebook.keys( )
for i in l:
if(cmp(i,name) == 0):
print “Phone number= “,phonebook[i]
f=l
if (f==0):
print “Given name not exist”
Output:
Enter total number of friends to create a telephone
book 5
enter name Ramu
enter phone number 9842311111
enter name Raju
enter phone number 9842309564
enter name Sarita
enter phone number 9842398765
enter name Sowmya
enter phone number 9842399922
enter name Karan
enter phone number 9842366554
enter friend’s name to search for Sarita
Phone number = 9842398765

Question 7:
Write the code to input any 5 years and the population of any city and print it on the screen.
Answer:
city=dict( )
n=5
i=l
while i<=n:
a=raw_input(” enter city name”)
b=raw_input(“enter population”)
city[a] =b
i=i+l
print city
Output :
enter city name Chennai
enter population 3400000
enter city name Mumbai
enter population 8900000
enter city name Bangalore
enter population 98700
enter city name Calicut
enter population 560000
enter city name Hyderabad
enter population 900000
{‘Bangalore’: ‘ 98700’/ Hyderabad’: ‘ 900000’, ‘ Chennai’: ‘ 3400000’, ‘ Mumbai’: ‘ 8900000’, ‘ Calicut’: ‘ 560000’}

Question 8:
Write a code to create customer’s list with their number & name and delete any particular customer using his /her number.
Answer:
customer=dict( )
n=input(” Enter total number of customers”)
i=l
while i<=n:
a=raw_input(“enter customer name”)
b=raw_input(“enter customer number”)
customer[a]=b
i=i+l
name=raw_input(” enter customer name to delete”)
del customer[name]
l=customer.keys( )
print “Customer Information”
print “Name”/\t’/’number”
for i in 1:
print i/\t’,customer[i]
Output :
Enter total number of customers 5
enter customer name Rohan
enter customer number 123678
enter customer name Ranjish
enter customer number 123677
enter customer name Suraj
enter customer number 123899
enter customer name Damu
enter customer number 123777
enter customer name Dhariya
enter customer number .123885
enter customer name to delete Suraj
Customer Information
Name number
Rohan   123678
Dhariya 123885
Ranjish   123677
Damu   123777

Question 9:
Find errors from the following codes:
c=dict( )
n=input(Enter total number) i=l
while i<=n
a=raw_input(“enter place”)
b=raw_input(” enter number”)
c(a)=b
i=i+l
print “place”,”\t”/’number”
for i in c:
print i,”\t”,cla[i]
Answer:
c=dict()
n=input(“Enter total number” )
i=l
while i<=n:
a=raw_input(“enter place”)
b=raw_input(“enter number”)
c[a]=b
i=i+l
print “place”,”\t”/”number”
for i in c:
print i.”\t”.c[il

NCERT Solutions for Class 11 Computer Science (Python) PDF

Unit 1 : Computer Fundamentals

Unit 2 : Programming Methodology

Unit 3 : Introduction to Python

Unit 4 : Programming with Python

12. Strings

NCERT Solutions Class 11 Computer Science (Python) Chapter-13 (Lists, Dictionaries and Tuples)