def get_isotope_dicts(element='', database='ENDF_VII'):
    """return a dictionary with list of isotopes found in database and name of database files
    
    Parameters:
    ===========
    element: string. Name of the element
      ex: 'Ag'
    database: string (default is ENDF_VII)
    
    Returns:
    ========
    dictionary with isotopes and files 
      ex: {'Ag': {'isotopes': ['107-Ag','109-Ag'],
                  'file_names': ['Ag-107.csv','Ag-109.csv']}}
    
    """
    _file_path = os.path.abspath(os.path.dirname(__file__))
    _database_folder = os.path.join(_file_path, 'reference_data', database)
    _element_search_path = os.path.join(_database_folder, element + '-*.csv')

    list_files = glob.glob(_element_search_path)
    if not list_files:
        raise ValueError("File names contains NO '-', the name should in the format of 'Cd-115_m1' or 'Cd-114'")
    list_files.sort()
    isotope_dict = {'isotopes': {'list': [],
                                 'file_names': [],
                                 'density': {'value': np.NaN,
                                             'units': 'g/cm3'},
                                 'mass': {'value': [],
                                          'units': 'g/mol',
                                          },
                                 'isotopic_ratio': [], },
                    'density': {'value': np.NaN,
                                'units': 'g/cm3'},
                    'molar_mass': {'value': np.NaN,
                                   'units': 'g/mol'},
                    }

    # isotope_dict_mirror = {}
    _isotopes_list = []
    _isotopes_list_files = []
    _isotopes_mass = []
    _isotopes_density = []
    _isotopes_atomic_ratio = []
    _density = np.NaN
    _molar_mass = np.NaN

    for file in list_files:
        # Obtain element, z number from the basename
        _basename = os.path.basename(file)
        filename = os.path.splitext(_basename)[0]
        if '-' in filename:
            [_name, _number] = filename.split('-')
            if '_' in _number:
                [aaa, meta] = _number.split('_')
                _number = aaa[:]
        else:
            _split_list = re.split(r'(\d+)', filename)
            if len(_split_list) == 2:
                [_name, _number] = _split_list
            else:
                _name = _split_list[0]
                _number = _split_list[1]
        if _number == '0':
            _number = '12'
        _symbol = _number + '-' + _name
        isotope = str(_symbol)

        _isotopes_list.append(isotope)
        _isotopes_list_files.append(_basename)
        _isotopes_mass.append(get_mass(isotope))
        _isotopes_atomic_ratio.append(get_abundance(isotope))
        _isotopes_density.append(get_density(isotope))
        _density = get_density(element)
        _molar_mass = get_mass(element)

    isotope_dict['isotopes']['list'] = _isotopes_list
    isotope_dict['isotopes']['file_names'] = _isotopes_list_files
    isotope_dict['isotopes']['mass']['value'] = _isotopes_mass
    isotope_dict['isotopes']['isotopic_ratio'] = _isotopes_atomic_ratio
    isotope_dict['isotopes']['density']['value'] = _isotopes_density
    isotope_dict['density']['value'] = _density
    isotope_dict['molar_mass']['value'] = _molar_mass
    return isotope_dict