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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}

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]

pos = 0 

sum = 0 

while pos < len (L): 

if L[pos] %2 = = 1 : 

sum = sum + L [pos] 

pos = pos + 1 

print sum 

Comma is used to separate the elements in the dictionary

The range( ) function has 3 arguments.

The list( ) function is used to create list in python

If the range is specified as [1 : 5], it will update the elements from 1 to 4

To delete an entire tuple, del command is used.

– is used to do difference in set

| operator joins two set

The position of an element is indexed with numbers beginning with 0

del statement deletes the entire list.

numlist = [ ]

evensum = 0

number = int(input(“Please enter the total no of list elements”))

for i in range(1, number +1):

value = int(input(“Please enter the value “)) 

numlist.append(value)

for j in range(number):

if(numlist[j]% 2 == 0):

even_sum = even_sum + numlist[j]

print(“Sum of even no. in this list = “ , even_sum) 

Output:

Please enter the total no of list elements : 5

Please enter the value : 10

Please enter the value : 11

Please enter the value : 12

Please enter the value : 13

Please enter the value : 14

The sum of even no. in this list = 60

In python, a list is simply created by using square bracket. The elements of list should be specified within square brackets. The following syntax explains the creation of list.

Syntax:

Variable = [element – 1, element – 2, element – 3 element – n]

Example:

Marks = [10, 23, 41, 75]

A list in Python is known as a “sequence data type” like strings. It is an ordered collection of values enclosed within square brackets [ ]. Each value of a list is called as element.

def reverse(list):

list.reverse( )

return list list = [10, 11, 12, 13, 14, 15] 

print(reverse(list))

Output:

15, 14, 13, 12, 11, 10

(a) 1-(iv), 2-(iii), 3-(i), 4-(ii)

[35, 45, 48, 71, 32, 29]

Using the range( ) function, you can create a list with series of values. To convert the result of range( ) function into list, we need one more function called list( ).

The list( ) function makes the result of range( ) as a list.

Syntax:

List_Varibale = list (range ( ))

marks = [10, 23, 41, 75]

append( ) function is used to add a single element in the list.

range function is used to generate a series of values in python

The function clear( ) is used to delete all the elements in list, it deletes only the elements and retains the list. Remember that, the del statement deletes entire list.

Answer is (d) :

(a) when new element is inserted in the list, the existing elements shift one position to the right

loop are used to access all elements from a list.

(i) pop( )

(ii) [ ] or empty square bracket

(d) negative

Join is called as union in sets

In Python, a tuple can be defined inside another tuple; called Nested tuple. In a nested tuple, each tuple is considered as an element. The for loop will be useful to access all the elements in a nested tuple.

Example:

Toppers = ((“Vinodini” , “XII-F”, 98.7), (“Soundarya” , “XII-H” , 97.5),

(“Tharani” , “XII-F”, 95.3), (“Saisri” , “XII-G” , 93.8)) 

for i in Toppers:

print(i)

Output:

(‘Vinodini’ , ‘XII-F’, 98.7)

(‘Soundarya’ , ‘XII-H’ , 97.5)

(‘Tharani’ , ‘XII-F’, 95.3)

(‘Saisri’ , ‘XII-G’ , 93.8)

(a) [34, 45, 48, 90]

In Python dictionary, del keyword is used to delete a particular element. The clear( ) function is used to delete all the elements in a dictionary. To remove the dictionary, we can use del keyword with dictionary name.

Dict={‘Roll No’: 12001, ‘SName’: ‘Meena’ , ‘Mark1’: 98, ‘Mar12’: 86}

print(“Dictionary elements before deletion: \n” , Dict) del Dict[‘Mark1’]

# Deleting a particular element Dict.clear( )

# Deleting all elements

(c) 75, 41, 23, 10

Answer is True

insert( ) function is used to insert an element at any position of a list.

index is used to access an element in a list

vowel = [‘a’ , ‘e’ , ‘i’ , ‘u’]

vowel.insert(3, ‘o’)

print(‘updated list’ , vowel)

Output:

updated list [‘a’ , ‘e’ , ‘i’ , ‘o’, ‘u’]

(i) The range( ) is a function used to generate a series of values in Python. Using range( ) function, you can create list with series of values. The range( ) function has three arguments.

Syntax of range( ) function: 

range (start value, end value, step value) where,

• start value – beginning value of series. Zero is the default beginning value.
• end value – upper limit of series. Python takes the ending value as upper limit – 1.
• step value – It is an optional argument, which is used to generate different interval of values.

Example: Generating whole numbers upto 10 for x in range (1, 11):

print(x)

Output

1

2

3

4

5

6

7

8

9

10

(ii) Creating a list with series of values Using the range( ) function, you can create a list with series of values. To convert the result of range( ) function into list, we need one more function called list( ). The list( ) function makes the result of range( ) as a list.

Syntax:

List_Varibale = list ( range ( ) )

Note

The list( ) function is all so used to create list in python.

Example

>>> Even_List = list(range(2,11,2))

>>> print(Even_List)

[2, 4, 6, 8, 10]

In the above code, list( ) function takes the result of range( ) as Even List elements. Thus, Even _List list has the elements of first five even numbers.

(iii) We can create any series of values using range( ) function. The following example explains how to create a list with squares of first 10 natural numbers.

Example: Generating squares of first 10 natural numbers

squares = [ ]

for x in range(1,11):

s = x ** 2

squares.append(s)

print (squares)

Output

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

& is intersection operator

n = [ ]

s = [ ]

for x in range(1, 51):

n.append(x)

for x in range(1, 51):

if(x%3 == 0) or (x % 6 == 0):

s.append(x)

print(“The numbers divisible by 3 or 6 is “ , s)

Output:

The numbers divisible by 3 or 6 is

[3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48]

a = [ ]

n = int(input”Enter number of elements :”))

for i in range(l, n+1):

b = int(input(“Enter element”))

a.append(b)

k = 0

num = int(input(“Enter the number to be counted : “)) for j in a:

if(j == num):

k = k+1

print(“Number of times” , num, “appears is” , k)

Output:

Enter number of elements : 4

Enter element: 23

Enter element: 45

Enter element: 23

Enter element: 67

Enter the number to be counted : 23

Number of times 23 appears is 2

= operator is used to change the list of elements

list=[2**x for x in range(5)

print(list)

[1, 2, 4, 8, 16]

A list in python is denoted by [ ]

Each value of a list is called as Element

append( ) function in Python is used to add more elements in a list. But, it includes elements at the end of a list. If you want to include an element at your desired position, you can use insert () function is used to insert an element at any position of a list.

Syntax:

List, insert (position index, element)

Example:

>>> MyList=[34,98,47, ‘Kannan’ , ‘Gowrisankar’ , ‘Lenin’ , ‘Sreenivasan’ ]

>>> print(MyList)

[34, 98, 47, ‘Kannan’ , ‘Gowrisankar’ , ‘Lenin’ , ‘Sreenivasan’]

>>> MyList.insert(3, ‘Ramakrishnan’)

>>> print(MyList)

[34, 98, 47, ‘Ramakrishnan’ , ‘Kannan’ , ‘Gowrisankar’ , ‘Lenin’ , ‘Sreenivasan’]

In the above example, insertf) function inserts a new element ‘Ramakrishnan’ at the index value 3, ie. at the 4th position. While inserting a new element in between the existing elements, at a particular location, the existing elements shifts one position to the right.