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Python | Unique values in Matrix

  • Last Updated : 25 Feb, 2019

Sometimes we need to find the unique values in a list, that is comparatively easy and has been discussed earlier. But we can also get a matrix as input i.e a list of lists, finding unique in them are discussed in this article. Let’s see certain ways in which this can be achieved.

Method #1 : Using set() + list comprehension
The set function can be used to convert the individual list to a non-repeating element list and the list comprehension is used to iterate to each of the lists.




# Python3 code to demonstrate
# checking unique values in matrix
# set() + list comprehension
  
# initializing matrix 
test_matrix = [[1, 3, 1], [4, 5, 3], [1, 2, 4]]
  
# printing the original matrix
print ("The original matrix is : " + str(test_matrix))
  
# using set() + list comprehension
# for checking unique values in matrix
res = list(set(i for j in test_matrix for i in j))
  
# printing result
print ("Unique values in matrix are : " + str(res))
Output:
The original matrix is : [[1, 3, 1], [4, 5, 3], [1, 2, 4]]
Unique values in matrix are : [1, 2, 3, 4, 5]

 
Method #2 : Using chain() + set()
The chain function performs the similar task that a list comprehension performs but in a faster way as it uses iterators for its internal processing and hence faster.




# Python3 code to demonstrate
# checking unique values in matrix
# chain() + set()
from itertools import chain
  
# initializing matrix 
test_matrix = [[1, 3, 1], [4, 5, 3], [1, 2, 4]]
  
# printing the original matrix
print ("The original matrix is : " + str(test_matrix))
  
# using chain() + set()
# for checking unique values in matrix
res = list(set(chain(*test_matrix)))
  
# printing result
print ("Unique values in matrix are : " + str(res))
Output:
The original matrix is : [[1, 3, 1], [4, 5, 3], [1, 2, 4]]
Unique values in matrix are : [1, 2, 3, 4, 5]

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