无法从数据帧中打印.copy（）之后的列表

Question

我声明了一个空列表_Xs_pred，然后尝试将单个列数据帧复制到列表中。该命令运行无误，但无法打印列表中的项目。 textual_data是单列数据框，其文本值是用空格连接的单词。我收到一个错误的“无法散列的列表”

a = {'all_terms': ['Bus Sys Analyst Sr IT Information Technology IT-Merchandising It Information Technology',
'Retail Sales Specialist Retail  Retail-Camping Retail Stores',
'Operations Specialist Retail  Retail-Stocking Retail Stores',
'Sales Lead Retail  Retail-Sales Lead Retail Stores',
'Retail Sales Specialist Retail  Retail-Cashier Retail Stores']}

textual_data = pd.DataFrame(data=a)

_Xs_pred =  [None, None]
report=True
model_levels = [True, True, True]
idx_col = ['Data Order']
_levels = ['Level-1', 'Level-2', 'Level-3']

for i in range(2):
    if model_levels[i]:
        textual_data.index.name = idx_col
        _Xs_pred[i] = textual_data.copy()
        if report:
            print("ETL complete on {} data."
            .format(_levels[i]))
    else:
        continue

print(_Xs_pred)

我希望输出为_Xs_pred，其中两列具有相同的textual_data。目前我看不到_Xs_pred