Algorithm Should Not Work

Below is a python program that performs an insertion sort. The main problem area is that "i" is changed within a loop the depends on i. This is very bad practice and will obviously lead to unexpected outcomes, but so far I have not been able to find an array that it does not work on. Can anyone figure out why it works?

def insertionSort(array): for i in range(1, len(array)): temp = array[i] tempPos = i-1 flag = False while flag == False and tempPos > -1: print(array) if temp < array[tempPos]: array[i] = array[tempPos] array[i-1] = temp tempPos = tempPos - 1 i = i - 1 else: flag = True