write a constant (uniform) template file

    Parameters
    ----------
    name : str
        the base parameter name
    tpl_file : str
        the template file to write - include path
    zn_array : numpy.ndarray
        an array used to skip inactive cells

    Returns
    -------
    df : pandas.DataFrame
        a dataframe with parameter information

def write_const_tpl(name, tpl_file, suffix, zn_array=None, shape=None, spatial_reference=None,
                    longnames=False):
    """ write a constant (uniform) template file

    Parameters
    ----------
    name : str
        the base parameter name
    tpl_file : str
        the template file to write - include path
    zn_array : numpy.ndarray
        an array used to skip inactive cells

    Returns
    -------
    df : pandas.DataFrame
        a dataframe with parameter information

    """


    if shape is None and zn_array is None:
        raise Exception("must pass either zn_array or shape")
    elif shape is None:
        shape = zn_array.shape

    parnme = []
    with open(tpl_file, 'w') as f:
        f.write("ptf ~\n")
        for i in range(shape[0]):
            for j in range(shape[1]):
                if zn_array is not None and zn_array[i, j] < 1:
                    pname = " 1.0  "
                else:
                    if longnames:
                        pname = "const_{0}_{1}".format(name,suffix)
                    else:
                        pname = "{0}{1}".format(name, suffix)
                        if len(pname) > 12:
                            raise("zone pname too long:{0}". \
                                               format(pname))
                    parnme.append(pname)
                    pname = " ~   {0}    ~".format(pname)
                f.write(pname)
            f.write("\n")
    df = pd.DataFrame({"parnme": parnme}, index=parnme)
    # df.loc[:,"pargp"] = "{0}{1}".format(self.cn_suffixname)
    df.loc[:, "pargp"] = "{0}_{1}".format(name, suffix.replace('_', ''))
    df.loc[:, "tpl"] = tpl_file
    return df