Python | Indices of Kth element value

Sometimes, while working with records, we might have a problem in which we need to find all the indices of elements for a particular value at a particular Kth position of tuple. This seems to be a peculiar problem but while working with many keys in records, we encounter this problem. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using loop

This is the brute force method by which this problem can be solved. In this, we keep a counter for indices and append to list if we find the specific record at Kth position in tuple.

# Python3 code to demonstrate working of
# Indices of Kth element value
# Using loop

# initialize list
test_list = [(3, 1, 5), (1, 3, 6), (2, 5, 7),
                        (5, 2, 8), (6, 3, 0)]

# printing original list
print("The original list is : " + str(test_list))

# initialize ele
ele = 3

# initialize K
K = 1

# Indices of Kth element value
# Using loop
# using y for K = 1
res = []
count = 0
for x, y, z in test_list:
    if y == ele:
        res.append(count)
    count = count + 1

# printing result
print("The indices of element at Kth position : " + str(res))

Output :

The original list is : [(3, 1, 5), (1, 3, 6), (2, 5, 7), (5, 2, 8), (6, 3, 0)]
The indices of element at Kth position : [1, 4]

Method #2 : Using enumerate() + list comprehension

The combination of above functions can be used to solve this problem. In this, we enumerate for the indices using enumerate(), rest is performed as in above method but in a compact way.

# Python3 code to demonstrate working of
# Indices of Kth element value
# Using enumerate() + list comprehension

# initialize list
test_list = [(3, 1, 5), (1, 3, 6), (2, 5, 7),
                        (5, 2, 8), (6, 3, 0)]

# printing original list
print("The original list is : " + str(test_list))

# initialize ele
ele = 3

# initialize K
K = 1

# Indices of Kth element value
# Using enumerate() + list comprehension
res = [a for a, b in enumerate(test_list) if b[K] == ele]

# printing result
print("The indices of element at Kth position : " + str(res))

Output :

The original list is : [(3, 1, 5), (1, 3, 6), (2, 5, 7), (5, 2, 8), (6, 3, 0)]
The indices of element at Kth position : [1, 4]