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Python | Convert a nested list into a flat list

  • Difficulty Level : Medium
  • Last Updated : 10 Sep, 2018

The task is to convert a nested list into a single list in python i.e no matter how many levels of nesting is there in python list, all the nested has to be removed in order to convert it to a single containing all the values of all the lists inside the outermost brackets but without any brackets inside.

Examples:

Input : l = [1, 2, [3, 4, [5, 6] ], 7, 8, [9, [10] ] ]
Output : l = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Input : l = [[[‘item1’, ‘item2’]], [[‘item3’, ‘item4’]]]
Output : l = [‘item1’, ‘item2’, ‘itm3, ‘item4”]

We use recursion because the levels of nesting cannot be predetermined.




# Python code to flat a nested list with
# multiple levels of nesting allowed.
  
# input list
l = [1, 2, [3, 4, [5, 6]], 7, 8, [9, [10]]]
  
# output list
output = []
  
# function used for removing nested 
# lists in python. 
def reemovNestings(l):
    for i in l:
        if type(i) == list:
            reemovNestings(i)
        else:
            output.append(i)
  
# Driver code
print ('The original list: ', l)
reemovNestings(l)
print ('The list after removing nesting: ', output)
Output:
The original list:  [1, 2, [3, 4, [5, 6]], 7, 8, [9, [10]]]
The list after removing nesting:  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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