def  bin_search(nums, target, left, right):
    """ Search the 'target' from the list 'nums'
    nums: a list of sorted numbers (could be strings as well)
    left: starting index of the list
    right: ending index of the list
    """
    if left > right:   # not found
        return False

    mid = (left + right) // 2
    if nums[mid] == target:
        return True
    elif nums[mid] < target:  # search for upper half
        left = mid + 1
        return bin_search(nums, target, left, right)
    else:
        right = mid -1        # search for lower half
        return bin_search(nums, target, left, right)

nums = [2, 5, 6, 7, 9, 10, 12]
print(bin_search(nums, 2, 0, len(nums)-1))    # True
print(bin_search(nums, 12, 0, len(nums)-1))   # True
print(bin_search(nums, 6, 0, len(nums)-1))    # True
print(bin_search(nums, 22, 0, len(nums)-1))   # False
print(bin_search(nums, 0, 0, len(nums)-1))    # False