Binary search for closest

def binary_search(sorted_list, value):
    left = 0
    right = len(sorted_list) - 1
    while left <= right:
        mid = (right + left) // 2
        if sorted_list[mid] == value:
            return mid    # found exact match
         # search value lies between current 2 items
        elif sorted_list[mid] < value and sorted_list[mid + 1] > value:
            if value - sorted_list[mid] == sorted_list[mid +1] - value:
                return mid
            elif value - sorted_list[mid] < sorted_list[mid +1] - value:
                return mid
            else:
                return mid + 1
        # keep looking
        elif sorted_list[mid] > value:
            right = mid - 1    # too high
        elif sorted_list[mid] < value:
            left = mid +1    # too low
# loop ends return `False`
    return False

list_of_numbers = [1, 2, 3, 5, 6, 7]
print("list of numbers is {}".format(list_of_numbers))

search_number = 3.5
print("Number to find is {}".format(search_number))

# 1st check first and last numbers in the list
last = len(list_of_numbers) - 1
# is number to find lower than 1st number in the sorted list
if list_of_numbers[0] > search_number:
    print("{} is not in the list".format(search_number))
# is number to find higher than last number in sorted list
elif list_of_numbers[last] < search_number:
    print("Largest number in list is {}".format(list_of_numbers[last]))
else :
    # call binary search
    item_at = binary_search(list_of_numbers, search_number)
# Display result of search
    if list_of_numbers[item_at] == search_number:
        # number has been found
        print("{} is in the list at posn {}".format(search_number, item_at))
    else:
        # only closest number found
        print("Closest number is {} at posn {}".format(list_of_numbers[item_at], item_at))