List methods in Python

• Difficulty Level : Easy
• Last Updated : 31 Mar, 2020

Python List
List Methods in Python | Set 1 (in, not in, len(), min(), max()…)
List Methods in Python | Set 2 (del, remove(), sort(), insert(), pop(), extend()…)

• append(): Used for appending and adding elements to List.It is used to add elements to the last position of List.
Syntax:
list.append (element)
 # Adds List Element as value of List.List = ['Mathematics', 'chemistry', 1997, 2000]List.append(20544)print(List)

Output:

['Mathematics', 'chemistry', 1997, 2000, 20544]

• insert(): Inserts an elements at specified position.
Syntax:
list.insert(<position, element)

Note: Position mentioned should be within the range of List, as in this case between 0 and 4, elsewise would throw IndexError.

 List = ['Mathematics', 'chemistry', 1997, 2000]# Insert at index 2 value 10087List.insert(2,10087)     print(List)

Output:

['Mathematics', 'chemistry', 10087, 1997, 2000, 20544]

• extend(): Adds contents to List2 to the end of List1.
Syntax:
List1.extend(List2)
 List1 = [1, 2, 3]List2 = [2, 3, 4, 5]  # Add List2 to List1List1.extend(List2)        print(List1)  # Add List1 to List2 nowList2.extend(List1) print(List2)

Output:

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

sum(), count(), index(), min() and max() functions of List

• sum() : Calculates sum of all the elements of List.
Syntax:
sum(List)
 List = [1, 2, 3, 4, 5]print(sum(List))

Output:

15

What happens if numeric value is not used a parameter?
Sum is calculated only for Numeric values, elsewise throws TypeError.
See example:

 List = ['gfg', 'abc', 3]print(sum(List))

Output:

Traceback (most recent call last):
File "", line 1, in
sum(List)
TypeError: unsupported operand type(s) for +: 'int' and 'str'

• count():Calculates total occurrence of given element of List.
Syntax:
List.count(element)
 List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]print(List.count(1))

Output:

4

• length:Calculates total length of List.
Syntax:
len(list_name)
 List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]print(len(List))

Output:

10

• index(): Returns the index of first occurrence. Start and End index are not necessary parameters.
Syntax:
List.index(element[,start[,end]])
 List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]print(List.index(2))

Output:

1

Another example:

 List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]print(List.index(2,2))

Output:

4

 List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]  """index(element, start, end) : It will calculate till index end-1. """  # will check from index 2 to 4.print("After checking in index range 2 to 4")print(List.index(2,2,5))  # will check from index 2 to 3.print("After checking in index range 2 to 3")print(List.index(2,2,4))

Output:

After checking in index range 2 to 4
4
After checking in index range 2 to 3
Traceback (most recent call last):
File "", line 1, in
List.index(2,2,4)
ValueError: tuple.index(x): x not in tuple

• min() : Calculates minimum of all the elements of List.
Syntax:
min(List)
 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]print(min(List))

Output:

1.054

• max(): Calculates maximum of all the elements of List.
Syntax:
max(List)
 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]print(max(List))

Output:

5.33

sort() and reverse() functions

• reverse(): Sort the given data structure (both tuple and list) in ascending order. Key and reverse_flag are not necessary parameter and reverse_flag is set to False, if nothing is passed through sorted().
Syntax:
sorted([list[,key[,Reverse_Flag]]])
list.sort([key,[Reverse_flag]])
 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]  #Reverse flag is set TrueList.sort(reverse=True)   #List.sort().reverse(), reverses the sorted list  print(List)

Output:

[5.33, 4.445, 3, 2.5, 2.3, 1.054]

 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]sorted(List)print(List)

Output:

[1.054, 2.3, 2.5, 3, 4.445, 5.33]

Deletion of List Elements

To Delete one or more elements, i.e. remove an element, many built in functions can be used, such as pop() & remove() and keywords such as del.

• pop(): Index is not a necessary parameter, if not mentioned takes the last index.
Syntax:
list.pop([index])

Note: Index must be in range of the List, elsewise IndexErrors occurs.

 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]print(List.pop())

Output:

2.5

 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]print(List.pop(0))

Output:

2.3

• del() : Element to be deleted is mentioned using list name and index.
Syntax:
del list.[index]
 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]del Listprint(List)

Output:

[4.445, 3, 5.33, 1.054, 2.5]
• remove(): Element to be deleted is mentioned using list name and element.
Syntax:
list.remove(element)
 List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]List.remove(3)print(List)

Output:

[2.3, 4.445, 5.33, 1.054, 2.5]

This article is contributed by Piyush Doorwar. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.