Código não retorna a coluna

notas.nota
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-22-43892b0a3e7a> in <module>()
----> 1 notas.nota

/usr/local/lib/python3.6/dist-packages/pandas/core/generic.py in __getattr__(self, name)
   5134             if self._info_axis._can_hold_identifiers_and_holds_name(name):
   5135                 return self[name]
-> 5136             return object.__getattribute__(self, name)
   5137 
   5138     def __setattr__(self, name: str, value) -> None:

AttributeError: 'DataFrame' object has no attribute 'nota'