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# Python – Extracting Priority Elements in Tuple List

• Last Updated : 03 Jul, 2020

Sometimes, while working with Python Records, we can have a problem in which we need to perform extraction of all the priority elements from records, which usually occur as one of the binary element tuple. This kind of problem can have possible application in web development and gaming domains. Let’s discuss certain ways in which this task can be performed.

Input :
test_list = [(7, 1), (3, 2), (4, 6)]
prior_list = [1, 3, 4]
Output : [1, 3, 4]

Input :
test_list = [(7, 3), (3, 4), (1, 6)]
prior_list = [1, 3, 4]
Output : [3, 4, 1]

Method #1 : Using loop
This is brute force approach to solve this problem. In this, we iterate each element of the priority list and check for individual tuple, filter out the matching element and append to list.

 # Python3 code to demonstrate working of # Extracting Priority Elements in Tuple List# loop  # initializing listtest_list = [(5, 1), (3, 4), (9, 7), (10, 6)]  # printing original listprint("The original list is : " + str(test_list))  # initializing Priority list prior_list = [6, 4, 7, 1]  # Extracting Priority Elements in Tuple List# loopres = []for sub in test_list:    for val in prior_list:        if val in sub:            res.append(val)  # printing result print("The extracted elements are : " + str(res))
Output :

The original list is : [(5, 1), (3, 4), (9, 7), (10, 6)]
The extracted elements are : [1, 4, 7, 6]

Method #2 : Using List comprehension + index()
The combination of above functions can be used to solve this problem. In this, we perform the task of checking for required element from tuple using index() and priority comparison.

 # Python3 code to demonstrate working of # Extracting Priority Elements in Tuple List# Using List comprehension + index()  # initializing listtest_list = [(7, 1), (6, 4), (4, 7), (1, 6)]  # printing original listprint("The original list is : " + str(test_list))  # initializing Priority list prior_list = [6, 4, 7, 1]  # Extracting Priority Elements in Tuple List# Using List comprehension + index()res = [sub[0] if prior_list.index(sub[0]) < prior_list.index(sub[1])              else sub[1] for sub in test_list]  # printing result print("The extracted elements are : " + str(res))
Output :
The original list is : [(7, 1), (6, 4), (4, 7), (1, 6)]
The extracted elements are : [7, 6, 4, 6]

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