check if x is in [a, b] with just one comparison! (a <= x <= b)

in_range.py

def in_range(x, a, b):
    ''' checks if x is in [a, b] '''
    if x == a: return True
    u = (b - a) / (x - a)
    return u >= 1


if __name__ == "__main__":
    assert in_range(10, 1, 100)
    assert in_range(10, 9, 11)
    assert in_range(0, -1, 1)
    assert in_range(-1, -10, 0)
    assert in_range(1, 0, 1)
    assert in_range(1, .99, 1)

    assert not in_range(10, 8, 9)
    assert not in_range(10, 0, 9)
    assert not in_range(100, 1, 10)
    assert not in_range(10, 11, 100)

    print('All tests passed!')