Python – Elements with K lists similar index value

Sometimes, while working with data, we can have a problem in which we need to get elements which are similar in K lists in particular index. This can have application in many domains such as day-day and other domains. Lets discuss certain ways in which this task can be performed.

Method #1 : Using zip() + loop
This is brute way in which this task can be performed. In this, we iterate the loop in zipped list and compare with elements in particular index for similarity.

# Python3 code to demonstrate
# Elements with K lists similar index value
# using zip() + loop

# Initializing lists
test_list1 = [1, 3, 5, 7]
test_list2 = [1, 4, 8, 9]
test_list3 = [3, 7, 5, 10]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))
print("The original list 3 is : " + str(test_list3))

# Initializing K
K = 2

# Elements with K lists similar index value
# using zip() + loop
res = []
for a, b, c in zip(test_list1, test_list2, test_list3):
    if a == b or b == c or c == a:
        if a == b:
            res.append(a)
        elif b == c:
            res.append(b)
        elif c == a:
            res.append(c)

# printing result
print ("The list after checking on 2 lists : " + str(res))

Output :

The original list 1 is : [1, 3, 5, 7]
The original list 2 is : [1, 4, 8, 9]
The original list 3 is : [3, 7, 5, 10]
The list after checking on 2 lists : [1, 5]

Method #2 : Using list comprehension + set() + count()
The combination of above methods can also be used to perform this task. In this, we check for count using count() and rest of functionalities are performed using list comprehension.

# Python3 code to demonstrate
# Elements with K lists similar index value
# using list comprehension + count() + set()

# Initializing lists
test_list1 = [1, 3, 5, 7]
test_list2 = [1, 4, 8, 9]
test_list3 = [3, 7, 5, 10]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))
print("The original list 3 is : " + str(test_list3))

# Initializing K
K = 2

# Elements with K lists similar index value
# using list comprehension + count() + set()
res = [ele for sub in zip(test_list1, test_list2, test_list3) for ele in set(sub) if sub.count(ele) > 1]

# printing result
print ("The list after checking on 2 lists : " + str(res))

Output :

The original list 1 is : [1, 3, 5, 7]
The original list 2 is : [1, 4, 8, 9]
The original list 3 is : [3, 7, 5, 10]
The list after checking on 2 lists : [1, 5]