Given Matrix, the following program shows how to extract all rows which have a pair such that their sum is equal to a specific number, here denoted as K.
Input : test_list = [[1, 5, 3, 6], [4, 3, 2, 1], [7, 2, 4, 5], [6, 9, 3, 2]], k = 8
Output : [[1, 5, 3, 6], [6, 9, 3, 2]]
Explanation : 5 + 3 = 8 and 6 + 2 = 8.
Input : test_list = [[1, 5, 4, 6], [4, 3, 2, 1], [7, 2, 4, 5], [6, 9, 3, 7]], k = 8
Output : []
Explanation : No list with 8 as pair summation.
Method 1 : Using loop and list comprehension
In this we perform the task of getting all the pair whose sum is equal to a given value using external function and filtering of lists is done using list comprehension.
Python3
# get pair sum def pair_sum(x, k): # checking pair sum for idx in range ( len (x)): for ix in range (idx + 1 , len (x)): if x[idx] + x[ix] = = k: return True return False # initializing list test_list = [[ 1 , 5 , 3 , 6 ], [ 4 , 3 , 2 , 1 ], [ 7 , 2 , 4 , 5 ], [ 6 , 9 , 3 , 2 ]] # printing original list print ( "The original list is : " + str (test_list)) # initializing K k = 8 # checking for pair sum res = [ele for ele in test_list if pair_sum(ele, k)] # printing result print ( "Filtered Rows : " + str (res)) |
Output:
The original list is : [[1, 5, 3, 6], [4, 3, 2, 1], [7, 2, 4, 5], [6, 9, 3, 2]]
Filtered Rows : [[1, 5, 3, 6], [6, 9, 3, 2]]
Method 2 : Using filter() and lambda
In this, we perform task of filtering using filter() and lambda function.
Python3
# get pair sum def pair_sum(x, k): # checking pair sum for idx in range ( len (x)): for ix in range (idx + 1 , len (x)): if x[idx] + x[ix] = = k: return True return False # initializing list test_list = [[ 1 , 5 , 3 , 6 ], [ 4 , 3 , 2 , 1 ], [ 7 , 2 , 4 , 5 ], [ 6 , 9 , 3 , 2 ]] # printing original list print ( "The original list is : " + str (test_list)) # initializing K k = 8 # checking for pair sum # filtering using filter() and lambda res = list ( filter ( lambda ele: pair_sum(ele, k), test_list)) # printing result print ( "Filtered Rows : " + str (res)) |
Output:
The original list is : [[1, 5, 3, 6], [4, 3, 2, 1], [7, 2, 4, 5], [6, 9, 3, 2]]
Filtered Rows : [[1, 5, 3, 6], [6, 9, 3, 2]]
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