Initialising nested classes in Python

Question

Let's say I want to create a class 'House' that has some attributes of its own, but also has a (nested?) 'Resident' class which has some attributes and has a mandatory attribute 'surname'. A house instance may exist though without any residents. How can create this so that I can eventually do the following?

myhouse = House()
residentX = myhouse.resident('Smith')

Currently I set this up as a nested class but run into trouble when I try and initialise myhouse given that it is requiring a surname at this point for the nested Resident class (which I don't necessarily have at this point)

class House:
 def __init__(self):
 self.someattribute = <someattribute>
 self.resident = self.Resident()
 class Resident:
 def __init__(self, surname):
 self.surname = surname

I know I can restructure the code to not use nested classes and then explicitly tie any resident to a house in my code. However, I would like to use the dot notation here (myhouse.resident) to automatically tie a resident to a house.

Also, I understand that nested classes in python are somewhat frowned upon - I'm open to suggestions on how to do the above in a more pythonic manner.

Answer 1

I would break out the Resident class and use a property/setter for .resident

Like this:

class House:
 def __init__(self):
 self.someattribute = <someattribute>
 self._resident = None
 @property
 def resident(self):
 return self._resident
 @resident.setter
 def resident(self, surname):
 r = Resident(surname)
 self._resident = r
class Resident:
 def __init__(self, surname):
 self.surname = surname

However, if you want .resident to be callable but also want to track the house's residents, you can still break out the Resident class, and use:

class House:
 def __init__(self):
 self.someattribute = <someattribute>
 self.residents = []
 def resident(self, surname):
 '''
 Add a resident to the house
 '''
 r = Resident(surname)
 self.residents.append(r)
 return r
class Resident:
 def __init__(self, surname):
 self.surname = surname

• GerryDevine: Yep, that second one is what I needed. Thanks.