import pickle


def save_variable(v, filename):
    """
    Save the variables in a file.

    Parameters
    ----------
    v : a list of variables to save.
    filename : specify a file name to save.

    Returns
    -------
    filename : the name of the saved file.

    """
    f = open(filename, 'wb')
    pickle.dump(v, f)
    f.close()
    return filename