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Python | Uncommon elements in Lists of List
  • Last Updated : 27 Feb, 2020

This particular article aims at achieving the task of finding uncommon two list, in which each element is in itself a list. This is also a useful utility as this kind of task can come in life of programmer if he is in the world of development. Lets discuss some ways to achieve this task.

Method 1 : Naive Method
This is the simplest method to achieve this task and uses the brute force approach of executing a loop and to check if one list contains similar list as of the other list, not including that.




# Python 3 code to demonstrate 
# Uncommon elements in List
# using naive method
  
# initializing lists
test_list1 = [ [1, 2], [3, 4], [5, 6] ]
test_list2 = [ [3, 4], [5, 7], [1, 2] ]
  
# printing both lists 
print ("The original list 1 : " + str(test_list1))
print ("The original list 2 : " + str(test_list2))
  
# using naive method 
# Uncommon elements in List
res_list = []
for i in test_list1:
    if i not in test_list2:
        res_list.append(i)
for i in test_list2:
    if i not in test_list1:
        res_list.append(i)
          
# printing the uncommon
print ("The uncommon of two lists is : " + str(res_list))
Output :
The original list 1 : [[1, 2], [3, 4], [5, 6]]
The original list 2 : [[3, 4], [5, 7], [1, 2]]
The uncommon of two lists is : [[5, 6], [5, 7]]

 

Method 2 : Using set() + map() and ^
The most efficient and recommended method to perform this task is using the combination of set() and map() to achieve it. Firstly converting inner lists to tuples using map, and outer lists to set, use of ^ operator can perform the set symmetic difference and hence perform this task. Further if it is required to get in lists of list fashion, we can convert outer and inner containers back to list using map().






# Python 3 code to demonstrate 
# Uncommon elements in Lists of List
# using map() + set() + ^
  
# initializing lists
test_list1 = [ [1, 2], [3, 4], [5, 6] ]
test_list2 = [ [3, 4], [5, 7], [1, 2] ]
  
# printing both lists 
print ("The original list 1 : " + str(test_list1))
print ("The original list 2 : " + str(test_list2))
  
# using map() + set() + ^
# Uncommon elements in Lists of List
res_set = set(map(tuple, test_list1)) ^ set(map(tuple, test_list2))
res_list = list(map(list, res_set))
  
# printing the uncommon 
print ("The uncommon of two lists is : " + str(res_list))
Output :
The original list 1 : [[1, 2], [3, 4], [5, 6]]
The original list 2 : [[3, 4], [5, 7], [1, 2]]
The uncommon of two lists is : [[5, 6], [5, 7]]

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