quick implementation of binary search in recursive python

recursive_bsearch.py

# Not efficient - this is better done as a while loop (unless Python can optimize tail-recursion...)
# return index of item.
# assumes arry is in ascending order.
# return -1 if item is not found in the array.
# interestingly, the bug I had where line 10 had high - low/ 2 still gave correct answers because the array was so small (and 
# perhaps also it was the dimensions?
def bsearch(arry, low, high, item):
  if low > high:
    return -1 # not found
  mid = high + low // 2
  if item == arry[mid]:
    return mid
  if item < arry[mid]:
    return bsearch(arry, low, mid-1, item)
  else:
    return bsearch(arry, mid+1, high,  item)

a = [1,3,5,6,7,9]    
assert(2 ==bsearch(a, 0, len(a)-1, 5))
assert(-1 ==bsearch(a, 0, len(a)-1, 4))  
assert(5 ==bsearch(a, 0, len(a)-1, 9))  # should be 5
assert(0 ==bsearch(a, 0, len(a)-1, 1))  # should be 0
print("passed unit tests")