问IndexError:至少必须有一个工作表是可见的

EN

 def multiple_dfs(sheet, row=2):

    writer = pd.ExcelWriter("testing.xlsx", engine='openpyxl')

    f1 = {
        'user': ['Bob', 'Jane', 'Alice'], 
        'income': [40000, 50000, 42000],
    }

    f2 = {
        'amount': ['Chest', 'Bras', 'Braa'], 
        'income': [40000, 50000, 42000]
    }

    frames = [f1, f2]


    for f in frames:
        try:
            wb = load_workbook("testing.xlsx")
            ws = wb.get_sheet_by_name("aaa")

            writer.wb = wb
            writer.sheets = dict((ws.title, ws) for ws in wb.worksheets)

            row = ws.max_row + 2
        except:
            pass 

        df = pd.DataFrame(f)
        df.to_excel(writer, sheet, startrow=row, index=False)
        writer.save()
    # writer.close()

multiple_dfs('aaa')

Traceback (most recent call last):
  File "create_and_update_xlsx_sheets.py", line 144, in <module>
    create_and_update_worksheets()
  File "create_and_update_xlsx_sheets.py", line 140, in create_and_update_worksheets
    writer.save()
  File "/home/jeremie/.virtualenvs/NHL/lib/python3.5/site-packages/pandas/io/excel.py", line 824, in save
    return self.book.save(self.path)
  ...
  File "/home/jeremie/.virtualenvs/NHL/lib/python3.5/site-packages/openpyxl/writer/workbook.py", line 61, in get_active_sheet
    raise IndexError("At least one sheet must be visible")
IndexError: At least one sheet must be visible