def pt_scale(pt=(0.0, 0.0), f=1.0):
    """Return given point scaled by factor f from origin.
    """
    assert isinstance(pt, tuple)
    l_pt = len(pt)
    assert l_pt > 1
    for i in pt:
        assert isinstance(i, float)
    assert isinstance(f, float)
    return tuple([(pt[i] * f) for i in range(l_pt)])
