como buscar la posicion [4,5,10,15,20,25,30,35,40,45,50,58,65,80,98]

def binary_search(list, value):
  low = 0
  high = len(list) - 1
 
  while low <= high:
    mid = (low + high) / 2
    midValue = list[mid]
    if midValue < value:
      low = mid + 1
    elif midValue > value:
      high = mid - 1
    else:
      return mid
 
  return -1
 
list = [4,5,10,15,20,25,30,35,40,45,50,58,65,80,98]
print binary_search(list, 50)