Python | Ways to flatten a 2D list

Given a 2D list, write a Python program to convert the given list into a flattened list.

Method #1: Using chain.iterable()

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# Python code to demonstrate 
# converting 2d list into 1d list
# using chain.from_iterables
  
# import chain
from itertools import chain
  
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
              
# printing initial list
print ("initial list ", str(ini_list))
  
# converting 2d list into 1d
# using chain.from_iterables
flatten_list = list(chain.from_iterable(ini_list))
  
# printing flatten_list
print ("final_result", str(flatten_list))

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Output:

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]

 
Method #2: Using list comprehension

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# Python code to demonstrate 
# converting 2d list into 1d list
# using list comprehension
  
# import chain
from itertools import chain
  
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
              
# printing initial list
print ("initial list ", str(ini_list))
  
# converting 2d list into 1d
# using list comprehension
flatten_list = [j for sub in ini_list for j in sub]
  
# printing flatten_list
print ("final_result", str(flatten_list))

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Output:

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]

 
Method #3: Using functools.reduce

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# Python code to demonstrate 
# converting 2d list into 1d list
# using functools.reduce
  
# import functools
from functools import reduce
  
ini_list = [[1, 2, 3],
            [3, 6, 7],
            [7, 5, 4]]
              
# printing initial list
print ("initial list ", str(ini_list))
  
# converting 2d list into 1d
# using functools.reduce
flatten_list = reduce(lambda z, y :z + y, ini_list)
  
# printing flatten_list
print ("final_result", str(flatten_list))

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Output:

initial list  [[1, 2, 3], [3, 6, 7], [7, 5, 4]]
final_result [1, 2, 3, 3, 6, 7, 7, 5, 4]


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