sub-attribute of attribute in python

Question

Similar question to this, I was wondering what is the right/common way to implement attribute of an attribute in python. Or I am wrong already with such a thought. Here are the examples:

method 1

It's obvious that it doesn't allow self.father.height

class household:
    def __init__(self, address, name0, height0, name1,height1 ):
        self.address = address
        self.father.name = name0
        self.father.height = height0
        self.mother.name = name1
        self.mother.height = height1

household("198 Ave", "John", 6.4, "Jean",5.2)

output:
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-180-09f6784cb40e> in <module>
----> 1 household("198 Ave", "John", 6.4, "Jean",5.2)

<ipython-input-179-9ccb52cdb476> in __init__(self, address, name0, height0, name1, height1)
      2     def __init__(self, address, name0, height0, name1,height1 ):
      3         self.address = address
----> 4         self.father.name = name0
      5         self.father.height = height0
      6         self.mother.name = name1

AttributeError: 'household' object has no attribute 'father'

method 2

It works well by using a dictionary without the attribute of an attribute, but I tend to use method 1 although it does not work for some reason.

class household:
    def __init__(self, address, name0, height0, name1,height1 ):
        self.address = address
        self.father = {"name":name0,"height":height0}
        self.mother = {"name":name1,"height":height1}

household("198 Ave", "John", 6.4, "Jean",5.2)

You can read about Classes and Object Oriented programming in python, will help you in this situations: https://docs.python.org/3/tutorial/classes.html — Damião Martins, Apr 01 '21 at 23:47
maybe, create a parent class and pass those object in a list and save the list in attibute name parent — sahasrara62, Apr 02 '21 at 00:02

bb1 · Answer 1 · 2021-04-02T04:49:22.857

It seems that you can get something close to what you intended using namedtuple:

from collections import namedtuple

class household:
    def __init__(self, address, name0, height0, name1, height1 ):
        self.address = address
        Parent = namedtuple('Parent', ['name', 'height'])
        self.father = Parent(name0, height0)
        self.mother = Parent(name1, height1)

Example:

h = household("198 Ave", "John", 6.4, "Jean",5.2)
print(h.father.name, h.father.height)

It gives:

John 6.4

score 1 · Accepted Answer · answered Apr 02 '21 at 03:38

1

what you need to do is that you first need to initialise self.father and then use self.father.name.

You should also read more about OOP from the python documentatoion

answered Apr 02 '21 at 03:38

Albert G Lieu · Answer 3 · 2021-04-02T20:04:54.037

I don't know which method is the typical/common way to implement it. But certainly, we can get method 1 to work. @angadsinghbedi is right, we can initialise self.father as an valid object with type("",(),{}). For more details about creating an empty object, see here

class household:
    def __init__(self, address, name0, height0, name1,height1 ):
        self.address = address
        self.father = type("person", (),{})()
        self.father.name = name0
        self.father.height = height0
        self.mother = type("person", (), {})()
        self.mother.name = name1
        self.mother.height = height1

house0 = household("198 Ave", "John", 6.4, "Jean",5.2)
house0.father.name
# John

score 0 · Answer 4 · answered Apr 01 '21 at 23:43

Method 1 doesn't work for exactly the reason the error message give you: you cannot create a sub-attribute for an attribute that doesn't exist. You would have to initialize self.father to something with a compatible structure; then your could assign to the child attributes.

Assigning the dict is a very good way to accomplish your desired result.

If I were to implement this, I would take the name/height pairs as a list or tuple of entries for later expansion. Some people have one parent; others have more than two.

household("198 Ave", [("John", 6.4), ("Jean",5.2)] )

thank you very much for sharing your knowledge – Albert G Lieu Apr 01 '21 at 23:59 — Albert G Lieu, Apr 01 '21 at 23:59

sub-attribute of attribute in python

4 Answers4