Python - Extract records if Kth elements not in List

Python – Extract records if Kth elements not in List

Difficulty Level : Basic
Last Updated : 29 Aug, 2020

Given list of tuples, task is to extract all the tuples where Kth index elements are not present in argument list.

Input : test_list = [(5, 3), (7, 4), (1, 3), (7, 8), (0, 6)], arg_list = [6, 8, 8], K = 1
Output : [(5, 3), (7, 4), (1, 3)]
Explanation : All the elements which have either 6 or 8 at 1st index are removed.
Input : test_list = [(5, 3), (7, 4)], arg_list = [3, 3, 3, 3], K = 1

Output : [(7, 4)]
Explanation : (5, 3) is removed as it has 3 at 1st index.

Method #1 : Using set() + loop

This is one way in which this task can be. In this, we shorten the argument list using set and then efficiently check for Kth index having any element from arg. list and append accordingly.

Python3

# Python3 code to demonstrate working of
# Extract records if Kth elements not in List
# Using loop
  
# initializing list
test_list = [(5, 3), (7, 4), (1, 3), (7, 8), (0, 6)]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing arg. list
arg_list = [4, 8, 4]
  
# initializing K
K = 1
  
# Using set() to shorten arg list
temp = set(arg_list)
  
# loop to check for elements and append
res = []
for sub in test_list:
    if sub[K] not in arg_list:
        res.append(sub)
  
# printing result
print("Extracted elements : " + str(res))

Output

The original list : [(5, 3), (7, 4), (1, 3), (7, 8), (0, 6)]
Extracted elements : [(5, 3), (1, 3), (0, 6)]

Method #2 : Using list comprehension + set()

This is yet another way in which this task can be performed. In this, we compile both, task of filtering duplicates using set() and compiling elements using conditionals inside list comprehension.

Python3

# Python3 code to demonstrate working of
# Extract records if Kth elements not in List
# Using list comprehension + set()
  
# initializing list
test_list = [(5, 3), (7, 4), (1, 3), (7, 8), (0, 6)]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing arg. list
arg_list = [4, 8, 4]
  
# initializing K
K = 1
  
# Compiling set() and conditionals into single comprehension
res = [(key, val) for key, val in test_list if val not in set(arg_list)]
  
# printing result
print("Extracted elements : " + str(res))

Output

The original list : [(5, 3), (7, 4), (1, 3), (7, 8), (0, 6)]
Extracted elements : [(5, 3), (1, 3), (0, 6)]

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