Your type check is incorrect, you're comparing a type to a string, use isinstance instead
if isinstance(i, list):type returns object of type class and you are comparing it to 'list' as string just change it like this:
l1 = [1, 2, [3, 4, 'Hello']]
for i in l1:
if type(i) is list:
for j in i:
print(j)for _ in range(int(input())):
name = input()
score = float(input())
marksheet += [
[name, score]
]
scorelist += [score]
scorelist = list(dict.fromkeys(scorelist))
b = sorted(scorelist)[1]
for a, c in sorted(marksheet):
if c == b:
print(a)a = [1, 2, 10, 9, [3, 4, "Hello"]]
b = []
for i in a:
if type(i) == type(b):
for j in i:
print(j)
else:
print(i)Last Updated : 08 Jun, 2020
The original list is: ['6', '89', ('7', ['8', '10']), ['11', '15']]
Data after type conversion: [6, 89, (7, [8, 10]), [11, 15]]The negative indexes for the items in a nested list are illustrated as below:,A list can contain any sort object, even another list (sublist), which in turn can contain sublists themselves, and so on. This is known as nested list.,A nested list is created by placing a comma-separated sequence of sublists.,You can access individual items in a nested list using multiple indexes.
L = ['a', ['bb', ['ccc', 'ddd'], 'ee', 'ff'], 'g', 'h']L = ['a', 'b', ['cc', 'dd', ['eee', 'fff']], 'g', 'h'] print(L[2]) # Prints['cc', 'dd', ['eee', 'fff']] print(L[2][2]) # Prints['eee', 'fff'] print(L[2][2][0]) # Prints eee
L = ['a', 'b', ['cc', 'dd', ['eee', 'fff']], 'g', 'h'] print(L[-3]) # Prints['cc', 'dd', ['eee', 'fff']] print(L[-3][-1]) # Prints['eee', 'fff'] print(L[-3][-1][-2]) # Prints eee
L = ['a', ['bb', 'cc'], 'd'] L[1][1] = 0 print(L) # Prints['a', ['bb', 0], 'd']
L = ['a', ['bb', 'cc'], 'd']
L[1].append('xx')
print(L)
# Prints['a', ['bb', 'cc', 'xx'], 'd']L = ['a', ['bb', 'cc'], 'd'] L[1].insert(0, 'xx') print(L) # Prints['a', ['xx', 'bb', 'cc'], 'd']
A nested list in python allows a list to contain multiple sublists within itself. Each sublist can have items of different data types. It can be created by placing comma-separated sublists and items together. Following is an example of a nested list in python satisfying the above-mentioned criteria.,In this tutorial, we will understand how to implement a nested List in Python. Before that let us understand list in Python. List in Python is a data type that can store multiple items of different data types into a single variable.,The following code explains how to access the horror category from the category sublist. Here we are accessing the first list. Within the first list, we want the second item which is again a sublist. Within that sublist, we want the second item.,One of the significant advantages of using lists over any other data type like tuples or string is that list is mutable. Therefore, an item inside the list can be easily changed or replaced with any other element. Following is an example of a simple list in python that stores a list of products displayed by any e-commerce website.
One of the significant advantages of using lists over any other data type like tuples or string is that list is mutable. Therefore, an item inside the list can be easily changed or replaced with any other element. Following is an example of a simple list in python that stores a list of products displayed by any e-commerce website.
products = ['books', 'toys', 'kitchenware']
print(f "Displaying products offered by our website: {products}")
print(f "Acessing 2nd product of list: {products[1]}")products=['books','toys','kitchenware']
print(f"Displaying products offered by our website: {products}")
print(f"Acessing 2nd product of list: {products[1]}")Output:
Displaying products offered by our website: ['books', 'toys', 'kitchenware']
Acessing 2n d product of list: toysA nested list in python allows a list to contain multiple sublists within itself. Each sublist can have items of different data types. It can be created by placing comma-separated sublists and items together. Following is an example of a nested list in python satisfying the above-mentioned criteria.
ecommerce = [
['books', ['comedy', 'horror'], 'toys', 'kitchenware'],
[200, 100, 350]
]
print(f "Displaying products offered by our website: {products}")The following code explains how to access the horror category from the category sublist. Here we are accessing the first list. Within the first list, we want the second item which is again a sublist. Within that sublist, we want the second item.
ecommerce = [
['books', ['comedy', 'horror'], 'toys', 'kitchenware'],
[200, 100, 350]
]
book_category = ecommerce[0][1][1]
print(f "Displaying second book category: {book_category}")ecommerce=[['books',['comedy','horror'],'toys','kitchenware'],[200,100,350]]
book_category=ecommerce[0][1][1]
print(f"Displaying second book category: {book_category}")Output: Displaying second book category: horror
Output: Category 0: comedy Category 1: horror
Output: [
['books', ['comedy', 'horror'], 'toys', 'clothes', 'kitchenware'],
[200, 100, 350]
]
[
['books', ['comedy', 'horror'], 'toys', 'clothes', 'kitchenware'],
[200, 100, 350],
['20%', '10%', '50%', '5%']
]['books', 'toys', 'clothes', 'kitchenware', 200, 100, 350]But I want you to also be aware because you will see this that you can mix and match your data types inside of a single list. So even though one of the most common ways that you'll see a list created is having all of the elements to have the same data type. You can change it up a bit and so let's do that here so I can say mixed list here. And the first element can be an integer.,However, when you're working with things such as large amounts of data or any kind of database query or anything like that then you want to try to keep each one of the elements in your list as uniform as possible so you can treat each one of them the same.,We can also even put lists inside of lists. So I could take this user list here paste it all in and if I run that you can see that we now have a list nested inside of another list,,and the cleaner way of doing it as opposed to putting all the elements in is actually storing it in the variable like we have right there. And now I have users here at the very last element and if I run this you can see that it slides the entire list of users right inside at the very end.
users = ['Kristine', 'Tiffany', 'Jordan', 'Leann']
ids = [1, 2, 3, 4]
mixed_list = [42, 10.3, 'Altuve', users]
print(mixed_list)
user_list = mixed_list.pop()
print(user_list)
print(mixed_list)
nested_lists = [
[123],
[234],
[345]
]Lists are useful data structures commonly used in Python programming. A nested list is a list of lists, or any list that has another list as an element (a sublist). They can be helpful if you want to create a matrix or need to store a sublist along with other data types.,Creating a matrix is one of the most useful applications of nested lists. This is done by creating a nested list that only has other lists of equal length as elements.,The length of the lists inside the nested list is equal to the number of columns.,Thus, each element of the nested list (matrix) will have two indices: the row and the column.
# creating list
nestedList = [1, 2, ['a', 1], 3]
# indexing list: the sublist has now been accessed
subList = nestedList[2]
# access the first element inside the inner list:
element = nestedList[2][0]
print("List inside the nested list: ", subList)
print("First element of the sublist: ", element)# create matrix of size 4 x 3
matrix = [
[0, 1, 2],
[3, 4, 5],
[6, 7, 8],
[9, 10, 11]
]
rows = len(matrix) # no of rows is no of sublists i.e.len of list
cols = len(matrix[0]) # no of cols is len of sublist
# printing matrix
print("matrix: ")
for i in range(0, rows):
print(matrix[i])
# accessing the element on row 2 and column 1 i.e.3
print("element on row 2 and column 1: ", matrix[1][0])
# accessing the element on row 3 and column 2 i.e.7
print("element on row 3 and column 2: ", matrix[2][1])For example, to create a list of lists of integer values, use [[1, 2], [3, 4]]. Each list element of the outer list is a nested list itself.,Definition: A list of lists in Python is a list object where each list element is a list by itself. Create a list of list in Python by using the square bracket notation to create a nested list [[1, 2, 3], [4, 5, 6], [7, 8, 9]].,Solution: Use two nested list comprehension statements, one to create the outer list of lists, and one to create the inner lists.,The list.reverse() reverses the order of the elements in the list. If you want to create a new list with reversed elements, use slicing with negative step size list[::-1].
For example, to create a list of lists of integer values, use [[1, 2], [3, 4]]. Each list element of the outer list is a nested list itself.
lst = [ [1, 2], [3, 4] ]
Find examples of all three methods in the following code snippet:
lst = [ [1, 2], [3, 4] ] # Method 1: List Comprehension flat_1 = [x for l in lst for x in l ] # Method 2: Unpacking flat_2 = [ * lst[0], * lst[1]] # Method 3: Extend Method flat_3 = [] for l in lst: flat_3.extend(l) # # Check results: print(flat_1) #[1, 2, 3, 4] print(flat_2) #[1, 2, 3, 4] print(flat_3) #[1, 2, 3, 4]
Solution: You can achieve this by using the beautiful (but, surprisingly, little-known) feature of dictionary comprehension in Python.
persons = [
['Alice', 25, 'blonde'],
['Bob', 33, 'black'],
['Ann', 18, 'purple']
]
persons_dict = {
x[0]: x[1: ]
for x in persons
}
print(persons_dict)
# {
'Alice': [25, 'blonde'],
# 'Bob': [33, 'black'],
# 'Ann': [18, 'purple']
}Here’s the alternative code:
persons = [
['Alice', 25, 'blonde'],
['Bob', 33, 'black'],
['Ann', 18, 'purple']
]
persons_dict = {}
for x in persons:
persons_dict[x[0]] = x[1: ]
print(persons_dict)
# {
'Alice': [25, 'blonde'],
# 'Bob': [33, 'black'],
# 'Ann': [18, 'purple']
}Example: Convert the following list of lists
[ [1, 2, 3], [4, 5, 6] ]
We will use list comprehension to iterate over a lists of list and then for each internal list again iterate over the individual elements in that list. Then add those elements to a new list i.e. ,We created a new empty list. Then using for loop we iterated over the list of lists, then for each internal list again iterated over the individual elements in that list. Then add those individual elements to a new list using list.append(),We created a new empty list. Then using for loop we iterated over the list of lists and then for each internal list appended its individual elements to our new flat list using list.extend().,Suppose we have a nested list that contain some number, some lists and these internal lists also contain some numbers & lists i.e.
Suppose we have a list of lists i.e.
# List of list listOfList = [ [1, 2, 3, 4, 5], [11, 22, 33, 44, 55], [17, 18, 19, 20, 21] ]
[1, 2, 3, 4, 5, 11, 22, 33, 44, 55, 17, 18, 19, 20, 21]We will use list comprehension to iterate over a lists of list and then for each internal list again iterate over the individual elements in that list. Then add those elements to a new list i.e.
# List of list
listOfList = [
[1, 2, 3, 4, 5],
[11, 22, 33, 44, 55],
[17, 18, 19, 20, 21]
]
# Use list comprehension to convert a list of lists to a flat list
flatList = [item
for elem in listOfList
for item in elem
]
print('Flat List : ', flatList)In python list data type provides a method to add an item at the end of a list,
list.append(x)
Suppose we have a nested list that contain some number, some lists and these internal lists also contain some numbers & lists i.e.
# Nested list
nestedList = [
[1, 2, 3],
[22, 33], 1, 3, 4,
[
[10, 11],
[222, 333,
[88, 99]
]
]
]