List in Python

The List are the another kind of data structure present in the python. They are more like arrays but they are not array.a list is created by placing all the items (elements) inside a square bracket [ ], separated by commas.It can have any number of items and they may be of different types (integer, float, string etc.).

#1.)Initializing an empty list.

a=[]

print(a)

# The output will be  [].

#Initializing a list with some elements.

a=[2,3,4]

print(a)

# The output will be  [2,3,4].

Another way of creating list is by list comprehension .we will see this point later.

# 2.) Indexing with List.

a=[2,3,4]

print(a[2])

#output : 4

#Negative Indexing :

a=[2,3,4]

print(a[-2])

#output : 3

# 3).Slicing in List

a=[2,3,4]

print(a[:2])

#output : [2,3]

a=[2,3,4,6,9,0,5]

print(a[2:4]) 

#output : [4, 6]

a=[2,3,4,6,9,0,5]

print(a[:])

#output : [2, 3, 4, 6, 9, 0, 5]

a=[2,3,4,6,9,0,5]

print(a[:-2])

#output :[2, 3, 4, 6, 9]

#4.) Nesting in List.

#We can create a list inside a list and there is no limit on the number of nesting.

a=[2,3,4,[6,9],0,5]

print(a[3])

#output : [6, 9]

a=[2,3,4,[6,9],0,5]

print(a[2:4])

#output : [4, [6, 9]]

#5.) Chnaging and updating a List.

#With the helpof assignment operator , we can be able to change the contents of a list unlike tuples.

a=[2,3,4,[6,9],0,5]

a[2] = 7

print(a)

#output : [2, 3, 7, [6, 9], 0, 5]

a=[2,3,4,[6,9],0,5]

a[2:4] = [7,5,6]

print(a)

#output : [2, 3, 7, 5, 6, 0, 5]


#We can also use + operator to combine two lists. This is also called concatenation.


a =[2,34,4]

b =[4,5,6]

print(a + b)

#output= [2, 34, 4, 4, 5, 6]

#The * operator repeats a list for the given number of times.

b =["san"]

print(b*3)

#output= ['san', 'san', 'san']


#Append in the List.

b =[2,3,4,5,6,7,8]
b.append(34)
print(b)

#output : [2, 3, 4, 5, 6, 7, 8, 34]

#count in the List.

b =[2,3,4,5,6,7,8,4]
print(b.count(4))

#output : 2

#Insert in the List at a specified index.

b =[2,3,4,5,6,7,8,4]
b.insert(4,4)
print(b)

#output :[2, 3, 4, 5, 4, 6, 7, 8, 4]

# Adding one List into another one.

a=[2,3,4]
b =[2,3,4,5,6,7,8,4]
b.extend(a)
print(b)

#output : [2, 3, 4, 5, 6, 7, 8, 4, 2, 3, 4]

#Note : There is no method in python which allow us to add a list in the specified position.

#Delete the first occurence of an element in python.

b =[2,3,4,5,6,7,8,4]
b.remove(4)
print(b)

#Output : [2, 3, 5, 6, 7, 8, 4]

#Index of first occurence of a number.

b =[2,3,4,5,6,7,8,4]

print(b.index(4))

#output : 2

Note : if the number is not available in the List , we will get a ValueError.

b =[2,3,4,5,6,7,8,4]

print(b.index(33))

#output : ValueError: 33 is not in list

#Sorting in the List.

b =[2,3,4,5,6,7,8,4]
b.sort()
print(b)

#Output : [2, 3, 4, 4, 5, 6, 7, 8]

#reverse  the order in the List.

b =[2,3,4,5,6,7,8,4]
b.reverse()
print(b)

#output : [4, 8, 7, 6, 5, 4, 3, 2]