python tutorial - Python List | List methods in Python - learn python - python programming




Adding and Appending

  • append(): Used for appending and adding elements to List.It is used to add elements to the last position of List.

Syntax:

python - Sample - python code :

list.append (element)
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python - Sample - python code :

# Adds List Element as value of List.
List = ['Mathematics', 'chemistry', 1997, 2000]
List.append(20544)
print(List)
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python programming - Output :

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

 

  • insert(): Inserts an elements at specified position.

Syntax:

python - Sample - python code :

list.insert(<position, element)
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Note: Position mentioned should be within the range of List, as in this case between 0 and 4, elsewise would throw IndexError.

python - Sample - python code :

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

['Mathematics', 'chemistry', 10087, 1997, 2000, 20544]
  • extend(): Adds contents to List2 to the end of List1.

Syntax:

python - Sample - python code :

List1.extend(List2)
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python - Sample - python code :

List1 = [1, 2, 3]
List2 = [2, 3, 4, 5]
 
# Add List2 to List1
List1.extend(List2)     
print(List1)
 
#Add List1 to List2 now
List2.extend(List1) 
print(List2)
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python programming - 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:

python - Sample - python code :

sum(List)
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python - Sample - python code :

List = [1, 2, 3, 4, 5]
print(sum(List))
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python programming - Output :

15

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

python - Sample - python code :

List = ['gfg', 'abc', 3]
print(sum(List))
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python programming - 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:

python - Sample - python code :

List.count(element)
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python - Sample - python code :

List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]
print(List.count(1))
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python programming - Output :

4
  • index(): Returns the index of first occurrence. Start and End index are not necessary parameters.

Syntax:

python - Sample - python code :

List.index(element[,start[,end]])
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python - Sample - python code :

List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]
print(List.index(2))
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python programming - Output :

1

Another example:

python - Sample - python code :

List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]
print(List.index(2,2))
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python programming - Output :

4

python - Sample - python code :

List = [1, 2, 3, 1, 2, 1, 2, 3, 2, 1]
 
# will check from index 2 to 3.
print(List.index(2,2,4))
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python - Sample - python code :

Traceback (most recent call last):
  File "", line 1, in 
    List.index(2,2,4)
ValueError: tuple.index(x): x not in tuple
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  • min() : Calculates minimum of all the elements of List.

Syntax:

python - Sample - python code :

min(List)
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python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
print(min(List))
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python programming - Output :

1.054
  • max(): Calculates maximum of all the elements of List.

Syntax:

python - Sample - python code :

max(List)
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python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
print(max(List))
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python programming - 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:

python - Sample - python code :

sorted([list[,key[,Reverse_Flag]]])
 list.sort([key,[Reverse_flag]])
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python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
 
#Reverse flag is set True
List.sort(reverse=True) 
 
#List.sort().reverse(), reverses the sorted list  
print(List)
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python programming - Output :

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

python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
sorted(List)
print(List)
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python programming - 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:

python - Sample - python code :

list.pop([index])
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Note: Index must be in range of the List, elsewise IndexErrors occurs.

python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
print(List.pop())
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python programming - Output :

2.5

python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
print(List.pop(0))
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python programming - Output :

2.3
  • del() : Element to be deleted is mentioned using list name and index.

Syntax:

python - Sample - python code :

del list.[index]
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python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
del List[0]
print(List)
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python programming - Output :

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

Syntax:

python - Sample - python code :

list.remove(element)
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python - Sample - python code :

List = [2.3, 4.445, 3, 5.33, 1.054, 2.5]
List.remove(3)
print(List)
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python programming - Output :

[4.445, 5.33, 1.054, 2.5]

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