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Convert List of Lists into a Flat List
To convert or transform a list of lists into a flat list, where the resulting list has the elements of the inner lists as elements, use List Comprehension or List.extend() method.
The syntax to use List Comprehension to flatten a list of lists is
[x for list_i in list_of_lists for x in list_i]The syntax to use List.extend() method to flatten a list of lists is
output = []
for e in list_of_lists:
output.extend(e)Examples
1. Flatten given List of Lists
In the following program, we take a list of lists, and use list comprehension to flatten a list of lists.
Python Program
list_of_lists = [
["apple", "banana", "cherry"],
[25, "mango", 44, 10],
["red", "green", "blue"]
]
output = [x for list_i in list_of_lists for x in list_i]
print(output)Output
['apple', 'banana', 'cherry', 25, 'mango', 44, 10, 'red', 'green', 'blue']2. Flatten given List of Lists using List.extend() Method
In the following program, we take a list of lists, and use List.extend() method to flatten a list of lists.
Iterate over each list in the list of lists, and extend the output list with each list in the for loop.
Python Program
list_of_lists = [
["apple", "banana", "cherry"],
[25, "mango", 44, 10],
["red", "green", "blue"]
]
output = []
for e in list_of_lists:
output.extend(e)
print(output)Output
['apple', 'banana', 'cherry', 25, 'mango', 44, 10, 'red', 'green', 'blue']Summary
In this Python Examples tutorial, we learned how to convert a list of lists into a single flattened list, using different approaches like list compression, and List.extend() method.