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Lists in Python

Jump to specific sections:

1. List indexing
2. List slicing
3. Lists are mutable
4. Lists Concatenation
5. Lists methods

Example:

# In this way we declare list
# lst1 is list containing only integers
lst1 = [1,2,3,4,5]

# lst2 contains different datatypes
lst2 = ["Rapid", 123, 11.23, False]

print(lst1)
print(type(lst1))
print(lst2)

Output:

[1, 2, 3, 4, 5]
<class 'list'>
['Rapid', 123, 11.23, False]

We can iterate over list using for loop in the following way:

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

for i in lst:
    print(i)

Output:

    1
    2
    3
    4
    5

Lists can be indexed in following way:

lst = ["Rapid","Coders","Akshay"]
# Every value of list can be accessed by its index
# list  = ["Rapid","Coders","Akshay"]
# index = [0,1,2]

# acessing value present at 0 index
print(lst[0])
print(lst[2])

print()
print("Now lets learn about negative index: ")
print("index of last element is -1")
print("index of last second element is -2 and so on")
print()
print(lst[-1])

Output:

Rapid
Akshay

Now lets learn about negative index: 
index of last element is -1
index of last second element is -2 and so on
    
    Akshay

Lists can be sliced, slicing means getting a part of a sequence.

Syantx:

    list_variable[Start_index : Stop_index]

Example:

lst = ["Rapid","Coders","Akshay"]

print("slicing from index 0 to 1",end=" = ")
print(lst[0:2])
print("slicing from index 1 to 2",end=" = ")
print(lst[1:2])

Output:

slicing from index 0 to 1 = ['Rapid', 'Coders']
slicing from index 1 to 2 = ['Coders']

Lists are mutable, this means we can change their content. Consider following example:

lst = ["Rapid","Coders","Akshay"]
print(lst)

# lets change element of list
lst[2] = "Developers"
print()
print(lst)

Output:

['Rapid', 'Coders', 'Akshay']

['Rapid', 'Coders', 'Developers']

Lists Concatenation: We can merge two lists into a single list using '+' operator.

lst1 = ["Rapid", "Coders"]
lst2 = ["Akshay", "Singh"]

print(lst1)
print(lst2)

print("lst1 + lst 2",end=" = ")
print(lst1 + lst2)

Output:

['Rapid', 'Coders']
['Akshay', 'Singh']
lst1 + lst 2 = ['Rapid', 'Coders', 'Akshay', 'Singh']

Lists methods:

1. lst.append(value): This method inserts value to the end of list.
2. lst.insert(index,value): This method inserts value at given index in list.
3. lst.pop(index): This will delete element which is present at given index.
4. lst.remove(value): This will remove given value from list.
5. lst.count(value): This will return the number of times value appears in the list.
6. lst.clear(): This will remove all elements from list.
7. lst.sort(): This sorts the list.
8. lst.reverse(): This reverses the list.

Code:

lst = ['Rapid', 'Coders', 'Akshay']
print(lst)
print()

lst.append("Singh")
print('lst.append("Singh")',end=" = ") 
print(lst)
print()

lst.insert(2,"I am")
print('lst.insert(2,"I am")',end=" = ")
print(lst)
print()
 
lst.pop(2)
print("lst.pop(2)",end=" = ")
print(lst)
print()

lst.remove("Akshay")
print('lst.remove("Akshay"',end=" = ")
print(lst)
print()
 
temp = lst.count("Rapid")
print('lst.count("Rapid")',end=" = ")
print(temp)
print()

lst.sort()
print("lst.sort()",end=" = ")
print(lst)
print()

lst.reverse()
print("lst.reverse()",end=" = ")
print(lst)
print()

lst.clear()
print("lst.clear()",end=" = ")
print(lst)

Output:

['Rapid', 'Coders', 'Akshay']

lst.append("Singh") = ['Rapid', 'Coders', 'Akshay', 'Singh']

lst.insert(2,"I am") = ['Rapid', 'Coders', 'I am', 'Akshay', 'Singh']

lst.pop(2) = ['Rapid', 'Coders', 'Akshay', 'Singh']

lst.remove("Akshay" = ['Rapid', 'Coders', 'Singh']

lst.count("Rapid") = 1

lst.sort() = ['Coders', 'Rapid', 'Singh']

lst.reverse() = ['Singh', 'Rapid', 'Coders']

lst.clear() = []