def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def torque(pos, torque, ax=0):
    """creates plot from torque vs position"""
    k = 20
    alpha = np.linspace(pos[0], pos[-1],
                        k*len(torque))
    f = ip.interp1d(pos, torque, kind='quadratic')
    unit = 'Nm'
    scale = 1
    if np.min(torque) < -9.9e3 or np.max(torque) > 9.9e3:
        scale = 1e-3
        unit = 'kNm'
    if ax == 0:
        ax = plt.gca()
    ax.set_title('Torque / {}'.format(unit))
    ax.grid(True)
    ax.plot(pos, [scale*t for t in torque], 'go')
    ax.plot(alpha, scale*f(alpha))
    if np.min(torque) > 0 and np.max(torque) > 0:
        ax.set_ylim(bottom=0)
    elif np.min(torque) < 0 and np.max(torque) < 0:
        ax.set_ylim(top=0)