Sequences and Lists in Python

In Python, a sequence is a set of ordered list. They are differentiated by their index number. The index starts from zero. Two basic types of sequence in Python are list and tuple.

Sequences and Lists in Python


Contents

  1. List
  2. List functions
  3. Tuple
  4. Tuple functions

 


1. Lists

  • For creating new list use square brackets.
  • In the list, it is not necessary that all list values should be of same Datatype (i.e, int, float, string,etc).
  • Lists are mutable or we easily modify existing list.

Creating a list

For creating a list, just put values between the square bracket and separated by commas.

Syntax –

[value1, value2, value3,...]
list1 = [1,2,3,4]
list2 = ["Sonarika","Vishal","Vijay","Aditya"]
list3 = ['h','e','l','l','0']
list4 = [4,"Jiten",'a',5]

Accessing list

For accessing values of the list, put index position inside square brackets.

Syntax –

list-variablename[index]

For slicing,

list-variablename[start-index : end-index]

start-index is from where to start selection, and end-index is index position where selection ends.

Example –

list1 = [1,2,3,4]
list2 = ["Sonarika","Vishal","Vijay","Aditya"]

print("list1[2] : ", list1[2])
print("list2[1:3] : ", list2[1:3])
print("list1[-2] : ",list1[-2])

When we execute the above program, it will produce the following output –

list1[2] : 3
list2[1:3] : ['Vishal', 'Vijay']
list1[-2] : 3

Updating list

For updating list, select index position and assign value using assignment operator (=).

list1 = [1,2,3,4]
list1[2] = 11
print(list1)

When we execute the above program, it will produce the following output –

[1,2,11,4]

Deleting list item

In Python, we can use del statement for deleting existing list or delete list item by index.

Syntax –

del list-name or del list-name[index]

Example –

list1 = [1,2,3,4]
del list1[2]
print(list1)

Output

[1,2,4]

List Functions

1. append – Adding a new value to existing list.
Syntax – append(value)

Example –

list1 = [1,2,3,4]
list1.append(32)
print(list1)

Output

[1,2,3,4,32]

2. count – Return the occurrence of value in existing list.
Syntax – count(value)

Example –

list1 = [1,2,3,4,3,43]
c = list1.count(3)
print(c)

Output

2

3. clear – Clear the existing list values.
Syntax – clear()

Example –

list1 = [43,3,22,11,54]
list1.clear()
print(list1)

Output

[]

4. extend – Adding sequence to existing list.
Syntax – extend(sequence)

Example –

list1 = [1,2,3,4]
list1.extend([5,6])
print(list1)

Output

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

5. insert – Insert value at given index.
Syntax – insert(index, value)

Example –

list1 = [1,2,3,4]
list1.insert(2,54)
list1.insert(5,11)
print(list1)

Output

[1,2,54,3,4,11]

6. index – Return the lowest index position of a value.
Syntax – index(value)

Example –

list1 = [1,2,3,2,4]
a = list1.index(2)
print("position : ",a)

Output

position : 1

7. pop – Remove the existing list value by index and return removing index value.
Syntax – pop(index)

Example –

list1 = [1,2,3,4]
print(list1[2])
print(list1)

Output

3
[1,2,4]

8. remove – Its also remove value from existing list by index, but it doesn’t return any value.
Syntax – remove(index)

Example –

list1 = [55,21,3,13,7]
list1.remove(2)
print(list1)

Output

[55,21,13,7]

9. reverse – Reverse the existing list.
Syntax – reverse()

Example –

list1 = [1,2,3,4]
list1.reverse()
print(list1)

Output

[4,3,2,1]

10. sort – Sort the existing list.
Syntax – sort()

Example –

list1 = [43,3,22,11,54]
list1.sort()
print(list1)

Output

[3, 11, 22, 43, 54]

Some others Functions

1. len – Return the total length of a list.

Syntax – len(list)

Example –

list1 = [43,3,22,11,54]
print("Length : ",len(list1))

Output

Length : 5

2. max – Return the max value from a list.

Syntax – max(list)

Example –

list1 = [43,3,22,11,54]
print("Max : ",max(list1))

Output

Max : 54

3. min – Return the min value from a list.

Syntax – min(list)

Example –

list1 = [43,3,22,11,54]
print("Min : ",min(list1))

Output

Min : 3

4. list – Convert a tuple into a list.

Syntax – list(seq)

Example –

tuple1 = (43,3,22,11,54)
list1 = list(tuple1)
print("tuple1 : ",tuple1)
print("list1 : ",list1)

Output

tuple1 : (43,3,22,11,54)
list1 : [43,3,22,11,54]

2. Tuple

  • For creating a new tuple use parentheses.
  • In tuple, it is not necessary that all values should be of same datatype (i.e, int, float, string,etc).
  • TuplesĀ are immutable or we can’t modify values of a tuple.

Creating a list

For creating a tuple, just put values between parentheses and separated by commas.

Syntax –

(value1,value2,value3,...)

Accessing a tuple

For accessing values of a tuple, put index position inside square brackets.

Syntax –

tuple-variablename[index]

For slicing,

tuple-variablename[start-index : end-index]

start-index is from where to start selection, and end-index is index position where selection ends.

Example –

tuple1 = [22,1,34,54]
tuple2 = ["Sonarika","Vishal","Vijay","Aditya"]

print("tuple1[2] : ", tuple1[2])
print("tuple2[1:3] : ", tuple2[1:3])
print("tuple1[-2] : ",tuple1[-2])

When we execute the above program, it will produce the following output –

tuple1[2] : 3
tuple2[1:3] : ['Vishal', 'Vijay']
tuple1[-2] : 34

Tuple Functions

1. count – Return the occurrence of value in existing tuple.
Syntax – count(value)

Example –

tuple1 = [12,1,54,41,1]
print("count : ",tuple1.count(1))

Output

count : 2

2. index – Return the lowest index position of a value.
Syntax – index(value)

Example –

tuple1 = [12,1,54,41,1]
print("position : ",tuple1.index(1))

Output

count : 2

Some others Functions

1. len – Return total length of a tuple.

Syntax – len(tuple)

Example –

tuple1 = (43,3,22,11,54)
print("Length : ",len(tuple1))

Output

Length : 5

2. max – Return max value from tuple.

Syntax – max(tuple)

Example –

tuple1 = [43,3,22,11,54]
print("Max : ",max(tuple1))

Output

Max : 54

3. min – Return min value from tuple.

Syntax – min(tuple)

Example –

tuple1 = [43,3,22,11,54]
print("Min : ",min(tuple1))

Output

Min : 3

4. tuple – Convert a list into a tuple.

Syntax – tuple(seq)

Example –

list1 = [43,3,22,11,54]
tuple1 = tuple(list1)
print("list1 : ",list1)
print("tuple1 : ",tuple1)

Output

list1 : [43,3,22,11,54]
tuple1 : (43,3,22,11,54)
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