helpers.py

#!/usr/bin/env python3
# -*- encoding: utf-8 -*-

def search(value, values):
    start = 0
    end = len(values) - 1

    result = bsearch(value, values, start, end)

    print("Number found: {}".format(result))

def bsearch(value, values, start, end):
    print("Search {} in {}...".format(value, values[start:end+1]))

    middle = (start + end) // 2

    current_value = values[middle]

    if current_value == value:
        return True
    elif current_value != value and start == end:
        return False
    elif current_value > value:
        print("Search left...")

        return bsearch(value, values, start, middle - 1)
    else:
        print("Search right...")

        return bsearch(value, values, middle + 1, end)

values = [1, 3, 6, 9, 10, 14, 16, 17, 21]

print("Testing the algorithm...")

for value in values:
    search(value, values)

search(7, values)