How to stop this while loop after it has run through a full array

I have this code that runs a loop, and it functions almost exactly how I want, except that I cannot get it to stop. Below is the relevant code:

while(True):
    try:
        # File to persist counter
        COUNTER_FILE = 'run_counter.txt'

        def get_next_element(arr):
            """Get next array element using persisted counter"""
        
            # Read existing counter or initialize
            if os.path.exists(COUNTER_FILE):
                with open(COUNTER_FILE, 'r') as f:
                    counter = int(f.read().strip())
            else:
                counter = 0

            # Get current element
            element = arr[counter % len(arr)]  # Use modulo for circular behavior
        
            # Update counter
            counter += 1
            with open(COUNTER_FILE, 'w') as f:
                f.write(str(counter))
        
            return element 

        # Example usage across multiple runs
        city_array = ['1', '2', '3']
        city = get_next_element(city_array)
        print(f"Assigned value: {city}")

<---- Some Code below that runs Selenium, works fine ---->

I understand that this sequence repeats on a forever loop because of while(True). I'm not sure what to change that loop to. I've also tried the simple solution:

print(f"Assigned value: {city}")
break

If I use the break in the above snippet, the counter will stop at the first element in this array:

city_array = ['1', '2', '3']

• What is happening: It runs the full city_array ['1', '2', '3'], or [0, 1, 2], then it runs it again, infinitely.

• What I want to happen: It runs the full city_array ['1', '2', '3'], or [0, 1, 2] -- then I want it to stop once it has run through the full array.

Answer

You can just check if "city" variable is at the last index of the array and break accordingly ie. if all elements are unique.

otherwise you can keep track of the current index and increment it everytime after the selenium code, once it becomes len(cities)-1 you can break the loop.