Python: Run class or element inside a class

Question

there is some way to execute a def that is within a class or some other element that I do not know about without the need to include the () of the class, only with the name? See the example below of how I wish it to work, if possible.

It need not necessarily be one class within another, it may be another element, but it is possible to execute in this way crud_regionalspc.CrudTabelaDados.select()

class CrudRegionalSPC:
    class CrudTabelaDados:
        def select(self):
            print("select")

        def delete(self):
            print("delete")


crud_regionalspc = CrudRegionalSPC()

# como funciona
crud_regionalspc.CrudTabelaDados().select()

# como eu gostaria que funcionasse
crud_regionalspc.CrudTabelaDados.select()

Answer 1

I have to say that it’s a very confusing and very biased structure to be a XY problem.

But by way of knowledge, by defining the method as static it will basically act as a normal function within the class, so there is no need for the self as parameter, since it will belong to the class and not to the instance.

class CrudRegionalSPC:
    class CrudTabelaDados:
        @staticmethod
        def select():
            print("select")

        @staticmethod
        def delete():
            print("delete")


crud_regionalspc = CrudRegionalSPC()

# como eu gostaria que funcionasse
crud_regionalspc.CrudTabelaDados.select()  # select

^{See working on Ideone}

Even you wouldn’t even need the instance to call the desired function:

CrudRegionalSPC.CrudTabelaDados.select()

Because then the classes would be acting basically as namespaces.

Answer 2

I don’t know exactly what you want to do, but there are some ideas:

Initially you can remove class nesting and instantiate a property:

class CrudTDados:
  def __init__(self, parent):
    self._parent = parent
    
  def select(self):
    print("select")

  def delete(self):
    print("delete")

 
class CrudRegionalSPC():   
  def __init__(self):
    self.CrudTabelaDados = CrudTDados(self)

    
crud_regionalspc = CrudRegionalSPC()

crud_regionalspc.CrudTabelaDados.select()

You can get the same result using decorators. Decorators can be functions or classes that add functionality to existing functions.

class CrudTDados:
  def __init__(self, parent):
    self._parent = parent
    
  def select(self):
    print("select")

  def delete(self):
    print("delete")

 
class CrudRegionalSPC():   
  @CrudTDados
  def CrudTabelaDados(self): pass


    
crud_regionalspc = CrudRegionalSPC()

crud_regionalspc.CrudTabelaDados.select()

You can also create an abstract class and subclass it. This way you can exchange these subclasses:

from abc import ABC, abstractmethod

class ICrud(ABC):
  @abstractmethod
  def select(self): pass
    
  @abstractmethod
  def delete(self): pass

class CrudMudo(ICrud):
  def select(self): pass
  def delete(self): pass

class CrudTDados(ICrud):
  def select(self):
    print("select Dados")

  def delete(self):
    print("delete Dados")

class CrudTClientes(ICrud):    
  def select(self):
    print("select Clientes")

  def delete(self):
    print("delete Clientes")

 
class CrudRegionalSPC():   
  def __init__(self, crud=CrudMudo()):
    self.CrudTabelaDados = crud;

  def MudarCrud(self, crud):
    self.CrudTabelaDados = crud

    
crud_regionalspc = CrudRegionalSPC()

crud_regionalspc.CrudTabelaDados.select()

crud_regionalspc.MudarCrud(CrudTClientes())

crud_regionalspc.CrudTabelaDados.select()

crud_regionalspc.MudarCrud(CrudTDados())

crud_regionalspc.CrudTabelaDados.select()