Instantiating views, models, and databases in MVC

I'm currently new to Python and am learning about the MVC architectural pattern. For simplicity sake and ease of explaining, let's say I have 3 classes. (Model, View, & Controller).

class Controller  
  def __init__(self):
    self.view = View()
    self.model = Model()

  def some_function(self):
    return self.model.add_things(1,2)

class Model
  def __init__(self):
    pass

  def add_things(self, x, y):
    return x + y

class View:
  def __init__(self):
    pass

Is it normal practice to instantiate my views and models as instance variables for the Controller as above?

Or is it better to import the files manually (i.e. import Model) at the top of Controller file and call the methods directly in the controller?

from Model import Model 
from View import View

class Controller  
  def __init__(self):
     pass

 def some_function(self):
     return Model.add_things(1, 2)

class Model
  def __init__(self):
    pass

  def add_things(self, x, y):
    return x + y

class View:
  def __init__(self):
    pass