The notation used when describing the speed of your Python program is called Big-O notation. Let's say you have a function:
def list_check(to_check, the_list): for item in the_list: if to_check == item: return True return False
This is a simple function to check if an item is in a list. To describe the complexity of this function, you will say O(n). This means "Order of n" as the O function is known as the Order function.
O(n) - generally n is the number of items in container
O(k) - generally k is the value of the parameter or the number of elements in the parameter