def binary_search(l, item):
    first = 0
    last = len(l)-1
    found = False

    while first<=last and not found:
        midpoint = round((first + last)/2)
        if l[midpoint] == item:
            found = True
        else:
            if item < l[midpoint]:
                last = midpoint-1
            else:
                first = midpoint+1

    return found

input = [0, 1, 2, 8, 13, 17, 19, 32, 42,]

print(binary_search(input, 3))   # found: False
print(binary_search(input, 13))  # fount: True