# Program 75: Find Index
def main():
    nums = list(map(int, input("Enter numbers: ").split()))
    target = int(input("Enter element: "))

    for i in range(len(nums)):
        if nums[i] == target:
            print("Index:", i)
            break

main()

Enter numbers:  1 2 3
Enter element:  123

# Program 76: Count Occurrence
def main():
    nums = list(map(int, input("Enter numbers: ").split()))
    target = int(input("Enter element: "))

    count = 0

    for n in nums:
        if n == target:
            count += 1

    print("Count:", count)

main()

Enter numbers:  1 2 3 4 5
Enter element:  12345


Count: 0

# Program 77: Replace Element
def main():
    nums = list(map(int, input("Enter numbers: ").split()))
    old = int(input("Old value: "))
    new = int(input("New value: "))

    for i in range(len(nums)):
        if nums[i] == old:
            nums[i] = new

    print("Updated list:", nums)

main()

Enter numbers:  6 7 8 7 6 
Old value:  1357
New value:  2478


Updated list: [6, 7, 8, 7, 6]