Python – Check if elements index are equal for list elements

Given two lists and check list, test if for each element in check list, elements occur in similar index in 2 lists.

Input : test_list1 = [2, 6, 9, 7, 8], test_list2 = [2, 7, 9, 4, 8], check_list = [9, 8, 7] Output : False Explanation : 7 is at 4th and 2nd place in both list, hence False. Input : test_list1 = [2, 6, 9, 7, 8], test_list2 = [2, 6, 9, 4, 8], check_list = [9, 8, 6] Output : True Explanation : All from checklist at similar index, hence True.

Method #1 : Using loop 

In this, we iterate for all the elements in list, if elements are different and is present in check list, then False is returned.

Python3

# Python3 code to demonstrate working of
# Check if elements index are equal for list elements
# Using loop

# initializing lists
test_list1 = [2, 6, 9, 7, 8]
test_list2 = [2, 7, 9, 4, 8]

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

# initializing check_list
check_list = [9, 8, 2]

res = True
for idx, ele in enumerate(test_list1):

    # check for indifference and containment
    if test_list1[idx] != test_list2[idx] and ele in check_list:
        res = False
        break

# printing result
print("Are elements at same index for required instances ?:  " + str(res))

Output

The original list 1 : [2, 6, 9, 7, 8]
The original list 2 : [2, 7, 9, 4, 8]
Are elements at same index for required instances ?:  True

Time Complexity: O(n), where n is the length of the input list. 
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the list “test_list”. 

Method #2 : Using zip() + all() + generator expression

In this, we pair like indices using zip() and then all() is used to check for all indices, generator expression is used for iteration logic.

Python3

# Python3 code to demonstrate working of
# Check if elements index are equal for list elements
# Using zip() + all() + generator expression

# initializing lists
test_list1 = [2, 6, 9, 7, 8]
test_list2 = [2, 7, 9, 4, 8]

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

# initializing check_list
check_list = [9, 8, 2]

# checking for all elements equal in check list using all()
res = all(a == b for a, b in zip(test_list1, test_list2) if a in check_list)

# printing result
print("Are elements at same index for required instances ?:  " + str(res))

Output

The original list 1 : [2, 6, 9, 7, 8]
The original list 2 : [2, 7, 9, 4, 8]
Are elements at same index for required instances ?:  True

Method#3:Using list comprehension

Python3

# initializing lists
test_list1 = [2, 6, 9, 7, 8]
test_list2 = [2, 7, 9, 4, 8]

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

# initializing check_list
check_list = [9, 8, 2]

# Using a list comprehension and the all function
# all returns True if all elements in the iterable are True, otherwise False
res = all(test_list1[i] == test_list2[i] for i in range(len(test_list1)) if test_list1[i] in check_list)

# printing result
print("Are elements at same index for required instances ?:  " + str(res))
#This code is contributed by Vinay Pinjala.

Output

The original list 1 : [2, 6, 9, 7, 8]
The original list 2 : [2, 7, 9, 4, 8]
Are elements at same index for required instances ?:  True

Time Complexity: O(n)

Auxiliary Space: O(n)