binary search in python
def binary_search_recursive(list_of_numbers, number, start=0, end=None):
# The end of our search is initialized to None. First we set the end to the length of the sequence.
if end is None:
end = len(list_of_numbers) - 1
if start > end:
# This will happen if the list is empty of the number is not found in the list.
raise ValueError('Number not in list')
mid = (start + end) // 2 # This is the mid value of our binary search.
if number == list_of_numbers[mid]:
# We have found the number in our list. Let's return the index.
return mid
if number < list_of_numbers[mid]:
# Number lies in the lower half. So we call the function again changing the end value to 'mid - 1' Here we are entering the recursive mode.
return binary_search_recursive(list_of_numbers, number, start, mid - 1)
# number > list_of_numbers[mid]
# Number lies in the upper half. So we call the function again changing the start value to 'mid + 1' Here we are entering the recursive mode.
return binary_search_recursive(list_of_numbers, number, mid + 1, end)