Python List Data Type

There are several Data types used in Python like

1. Strings
2. Tuple
3. Set
4. Dictionary
5. List

In this post, we are going to have a clear idea about List and its predefined modules.

The list is a mutable data type which means we can change memory Allocation based on our requirements and it is represented with square brackets [].list can accept any kind of data ex: int, float, string.

a = [1,1.2,'python',True] # boolean = True , False
for i in a:
    print(type(i))

using the index position we can access the values which are inside the list. for example, for accessing the value 1.2 its index is 1 so we can call it using logic a[1].

mylist = [4,9,6,2]
print(mylist[0])
print(mylist[1])
print(mylist[2])
print(mylist[3])

For accessing Multiple values we can use a concept called slicing operations. where the forward slicing index starts from 0 and in reverse slicing index starts from -1.

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

# from 2nd element till 5th element
print(mylist[1:5])

# from start till 5th element
print(mylist[:5])

# from 5th element till end
print(mylist[4:])

# from start till 3rd last element
print(mylist[:-2])

# from 4th last element till 3rd last element
print(mylist[-4:-2])

# from 3rd element till 3rd last element
print(mylist[2:-2])

# all elements
print(mylist[:])

mylist = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# from 2nd element till 9th element
print(mylist[1:9])

# from 2nd element till 9th element in step 2
print(mylist[1:9:2])

# from 2nd element till 9th element in step 3
print(mylist[1:9:3])

mylist = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

# from 3rd element till 9th element
print(mylist[2:9])

# from 3rd element till 9th element in step 2
print(mylist[2:9:2])

# from 3rd element till 9th element in step 3
print(mylist[2:9:3])

# from start till 9th element in step 2
print(mylist[:9:2])

# from 3rd element till end in step 3
print(mylist[2::3])

# elements from start till end in step 2
print(mylist[::2])

There are some predefined modules that help us to manipulate the values inside a list in Multiple ways.

1. append
2. clear
3. extend
4. pop
5. insert
6. del
7. remove
8. Membership function
9. sort
10. Math operations

• append is used to add the values at the end of the list.

#Adding Elements to Python List
#Adding a Single Element to Python List
mylist = [1, 2, 3, 4]
mylist.append(5)  # 5 is added to the list
print(mylist)  # printing changed list

• clear is used to remove clear the entire data from the list so it will be empty.

#Python clear()
colors = ["Blue", "Green", "Red", "Orange", "Yellow", "Brown"]
colors.clear()  # removing all element from list
print(colors)  # printing updated list 

• extend is used to add another list

a = [1, 2 , 3, 4]
a.extend([10,100])
print(a)

• pop is used to remove the last value from the list but if u specify any values it takes the value as an index and removes the index-located value.

a = [1, 2 , 3, 4]
a.pop()
#a.pop()
print(a)  # output = [1,2,3]

if we specify any value 

a = [1,2,3,4]
a.pop(2) 

output = [1,2,4] because 2nd index value is removed from the given list 

• Insert is used to add value where ever we want using the index concept

mylist = [1, 2, 3, 4]
mylist.insert(2, 5)  # adding 5 at index 2 of the list
print(mylist)  # printing changed list

• del keyword will delete the value from the list

colors = ["Blue", "Green", "Red", "Orange", "Yellow", "Brown"]
del colors[2:4]  # deleting from 3rd element to fourth element
print(colors)  # from 2nd till 3rd index values will be deleted using (n-1) concept 

• Instead of using index concepts every time we can use the remove function which directly takes the value and removes it from the given list.

#Python remove()
colors = ["Blue", "Green", "Red", "Orange", "Yellow", "Brown"]
colors.remove('Green')  # removing "Green" from list
print(colors)

# Green is removed from the given list 

• The membership function is useful for finding the specified value present in a given list or not. If it’s present means it returns true and if not it returns false.

#Python List Membership Test
mylist = [1, 2, "Blue", "Green"]
print(2 in mylist)  # True 
print(4 in mylist)  # False 
print("Green" not in mylist)  # True

• sort function helps us to sort values from ascending order to descending order or from descending order to ascending order.

a = [4,3,1,2]  # ascending order 
a.sort()
print(a)  # output = [1, 2, 3, 4]


a = [4,3,1,2]  # descending order 
a.sort(reverse = True)  # reverse = True makes sort in descending order 
print(a)  # output = [4, 3, 2, 1]

• Math Operations

mylist = [1, 2, 3, 4, 5, 6]
print(len(mylist))  # len keyword is used to find the number of values 
# Output = 6

mylist = [3, 2, 1, 5, 6, 4]  # max keyword used to find maximum value 
print(max(mylist))
# output = 6

mylist = [3, 2, 1, 5, 6, 4]  # min keyword used to find minimum value 
print(min(mylist))
# output = 1

For more code examples You can collect them from my GitHub page

https://github.com/saikamal3344/Medium-Blogs/blob/main/Python%20List.ipynb

a = [1,1.2,'python',True] # boolean = True , False
for i in a:
    print(type(i))