Lists

The most important data type in python is a list. The list stores the sequence of data. The list is mutable means we can modify, update, insert and delete the data. Each element in the list is assigned a number of its position or index. The first index is zero, the second is one and so forth.

 

Examples:

Fruits = [“oranges”, “grapes”, “bananas”, “mangoes”]
  Numbers = [1,2,3,4,5,6]
  Student = [{“name”:”sai”, “marks”:513}, {“name”:”ram”, “marks”:500}]
  Movies = [(‘guru’, ‘telugu’), (‘Aaru’, ‘tamil’)]
  We can also take all data types in a list.
  Data = [“oranges”, 1,2, {“name”:”sai”, “marks”:513}, (‘guru’, ‘telugu’),[1,2,3]]
  

How to access values from List?

fruits = ["oranges", "grapes", "bananas", "mangoes"]

print(fruits[0])

output: oranges.

Example2:

fruits = ["oranges", "grapes", "bananas", "mangoes"]

print(fruits[1:3])

output: ['grapes', 'bananas']

 

Example3:

fruits = ["oranges", "grapes", "bananas", "mangoes"]

print(fruits[-1])

 

output: mangoes

 

 

How to update list?

fruits = ["oranges", "grapes", "bananas", "mangoes"]

print("Before updating", fruits[1])

print(fruits)

print('----------------------------------------')

fruits[1] = 1

print('After updating', fruits[1])

print(fruits)

 

How to delete element from list?

fruits = ["oranges", "grapes", "bananas", "mangoes"]

print("Before deleting", fruits)

 

print('----------------------------------------')

del fruits[1]

print('After deleting', fruits)

 

output:

Before deleting ['oranges', 'grapes', 'bananas', 'mangoes']

----------------------------------------

After deleting ['oranges', 'bananas', 'mangoes']

 

List operations

 

How to find the length of a list?

 

There is a length function to find the length of a list and this function is most important to find data types length.

fruits = ["oranges", "grapes", "bananas", "mangoes"]

print("Length of a list", len(fruits))

output:

Length of a list 4

 

How to concatenate lists in python?

To concatenate lists in python, we can use + operator.

fruits = ["oranges", "grapes", "bananas", "mangoes"]

vegitables = ["tomato", "onions", "carrots", "potato"]

print(fruits + vegitables)

output:

['oranges', 'grapes', 'bananas', 'mangoes', 'tomato', 'onions', 'carrots', 'potato']

 

How to repeat list in twice or more?

fruits = ["oranges", "grapes", "bananas", "mangoes"] * 2

print(fruits)

 

output:

['oranges', 'grapes', 'bananas', 'mangoes', 'oranges', 'grapes', 'bananas', 'mangoes']

 

What is the search operator in lists?

'In' is a search operator in the list. If you want to search an element in a list you can use it 'in operator'.

fruits = ["oranges", "grapes", "bananas", "mangoes"]

 

if "grapes" in fruits:

    print('Fruit found')

else:

    print("Fruit not found")

output:

Fruit found

How to print lists element by using loops?

Using for loop:

fruits = ["oranges", "grapes", "bananas", "mangoes"]

 

for fruit in fruits:

    print(fruit)

output:

oranges

grapes

bananas

mangoes

using while loop:

fruits = ["oranges", "grapes", "bananas", "mangoes"]

 

while fruits:

    print(fruits.pop())

output:

mangoes

bananas

grapes

oranges

Built-in functions

Function	Description
fruits.append(obj)	It is used to append objects to list.
fruits.count(obj)	It is used to count how many times an item occurs in a given list.
fruits.extend(seq)	It is used to append a list to another list.
fruits.index(obj)	It is used to find the index value of an element.
fruits.insert(obj)	It is used to insert an element in a particular position.
fruits.pop(obj)	It is used to remove an element from list and returns removed element.
fruits.remove(obj)	It is used to remove a particular element.
fruits.reverse()	It is used to reverse the list. There is a short cut to reverse the list Ex: fruits = [“oranges”, “grapes”, “bananas”, “mangoes”] Print(fruits[::-1])
fruits.sort()	It is used to sort the list.