Python List: Declaring adding searching and removing elements

About	ordered	changeable	duplicate	Sample
list	ordered	changeable	allows	['abc','def','abc']
tuple	ordered	unchangeable	allows	('abc','def','abc')
set	unordered	unindexed	Not allows	{'abc','def','ghi'}
dictionary	unordered	changeable	Not allows	{'name':'King','Class':'four'}

Declaring a List

my_list=['Alex','Ronald','John']
print(my_list)

Output

['Alex','Ronald','John']

Unpacking and listing elements

print(*my_list)

Output

Alex Ronald John

Displaying elements based on position

my_list=['Alex','Ronald','John']
print(my_list[2])

Output is here

John

index() : Returning the first position of the input element.

my_list=['Ronald','John','Alex','Ravi','Alex']
print(my_list.index('Alex'))

Output is here

The position starts from 0 and first element value is my_list[0], so the data at my_list[2] gives us John.

my_list=['Ronald','John','King','Ravi','Alex']
print(my_list[-1]) # last element will be displayed : Alex
print(my_list[-2]) # 2nd from last element will be displayed : Ravi
print(my_list[0:])  # All elements starting from 0 position till end.
print(my_list[:3])  # All elements starting from 0 position till 3.
print(my_list[1:4])  # All elements starting from 1 position till 4.

Output is here

Alex
Ravi
['Ronald', 'John', 'King', 'Ravi', 'Alex']
['Ronald', 'John', 'King']
['John', 'King', 'Ravi']

We can go beyond the last element ( No error here )

print(my_list[1:8])  # All elements starting from 1 position till end.

Output

['John', 'King', 'Ravi', 'Alex']

Displaying all items by looping

We used for loop to display all items of the list.

my_list=['Alex','Ronald','John']
for i in my_list:
    print(i)

Output is here

Alex
Ronald
John

Add , remove , update elements

append()

my_list=['Alex','Ronald','John']
my_list.append('Ravi')
print(my_list)

Output is here

['Alex', 'Ronald', 'John', 'Ravi']

insert(): Adding at location

my_list=['Alex','Ronald','John']
my_list.insert(2,'Ravi')
print(my_list)

Output is here

['Alex', 'Ronald', 'Ravi', 'John']

extend() : Adding elements or list at the end of the list

my_list1=['Alex','Ronald','John']
my_list2=['Ravi','Alen']
my_list1.extend(my_list2)
print(my_list1)

Output is here

['Alex', 'Ronald', 'John', 'Ravi', 'Alen']

copy() : Creates new list by copying all elements

my_list1=['Alex','Ronald','John']
my_list2=my_list1.copy()
print(my_list2)

Output is here

['Alex', 'Ronald', 'John']

remove(): Deleting element

my_list=['Alex','Ronald','John']
my_list.remove('Ronald')
print(my_list)

Output is here

['Alex', 'John']

pop(): Deleting element based on location, by default it removes last element

my_list=['Alex','Ronald','John']
my_list.pop()  # deletes last element
print(my_list)

Output is here

['Alex', 'Ronald']

We can remove element from a perticular position

my_list=['Alex','Ronald','John']
my_list.pop(0)  # deletes first element
print(my_list)

Output is here

['Ronald', 'John']

We can collect the removed element

my_list=['Alex','Ronald','John']
name=my_list.pop(1)  # deletes first element
print(name)

Output is here

Ronald

clear() : Removing all elements

my_list=['Alex','Ronald','John']
my_list.clear()  # deletes all elements
print(my_list)

Output is here

[]

Searching element

my_list=['Alex','Ronald','John']
if 'John' in my_list:
  print("Yes, included ")
else:
  print("No, not included")

Output is here

Yes, included

Searching pair of numbers within a list

my_list=[[1,3],[3,4],[4,6]]
if [3,4] in my_list:
    print("yes present")
else:
    print("Not present")

output is here

yes present

Number of elements present:

count():Number of specified element present in a list ( counting the occurrence of a element )

my_list=['Alex','Ronald','John','Alex','Ravi','Alex']
print(my_list.count('Alex'))

Output is here

len() : Total Number of elements present in a list

my_list=['Alex','Ronald','John']
print("Number of elements:",len(my_list))

Output

Number of elements: 3

reverse() :Reverse the order of the list

my_list=['Ronald','John','Alex','Ravi']
my_list.reverse()
print(my_list)

Output

['Ravi', 'Alex', 'John', 'Ronald']

sort() : Sort the list in order

my_list=['Ronald','John','Alex','Ravi']
my_list.sort()
print(my_list)

Output

['Alex', 'John', 'Ravi', 'Ronald']

my_list=[4,2,7,1]
my_list.sort()
print(my_list)

Output is here

[1, 2, 4, 7]

Creating a list with distinct elements

We can use a set to store unique elements as set don't accept duplicate elements.

my_list=[1,2,3,4,4,5,5,6]
print(set(my_list))

Output

{1, 2, 3, 4, 5, 6}

Removing duplicate by using for loop

my_list=[1,2,3,4,4,5,5,6]
my_list2=[]
for i in my_list:
    if i not in my_list2:
        my_list2.append(i)
print(my_list2)

Output

[1, 2, 3, 4, 5, 6]

Getting unique elements and counting the occurrence by using Counter.

Sum of elements of a list

As list is an iterator Object , we can use sum to calculate sum of all elements.

my_list=[1,2,5,6]
my_list_sum=sum(my_list)
print(my_list_sum)
print("Sum by looping")
my_sum=0
for i in my_list:
    my_sum=my_sum+i
print(my_sum)

Output

14
Sum by looping
14

Common elements between two Lists

list1=[3,2,5,8]
list2=[5,2,8,9]
print(set(list1) & set(list2))

Output

{8, 2, 5}

Highest and lowest Common elements

print(max(set(list1) & set(list2)))
print(min(set(list1) & set(list2)))

Output

8
2

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LIST in Python

Declaring a List

Displaying all items by looping

Add , remove , update elements

Searching element

Number of elements present:

Creating a list with distinct elements

Sum of elements of a list

Common elements between two Lists