my_tuple = ((15, 16), (71), 42, 99)

print("The tuple is :")
print(my_tuple)

K = "Pyt"
print("The value of K is :")
print(K)

my_result = [element for sub in my_tuple for element in (sub, K)]

print("The result is :")
print(my_result)

The tuple is :
((15, 16), 71, 42, 99)
The value of K is :
Pyt
The result is :
[(15, 16), 'Pyt', 71, 'Pyt', 42, 'Pyt', 99, 'Pyt']