Series对象没columns属性，如何更改

Series对象没columns属性，如何更改，
Traceback (most recent call last):
File "C:\Users\于赛坤\Desktop\lesson7.py", line 57, in
EN = df_cashflow.columns.tolist()
File "C:\Users\于赛坤\venv\lib\site-packages\pandas\core\generic.py", line 5902, in getattr
return object.getattribute(self, name)
AttributeError: 'Series' object has no attribute 'columns'