Python Nesting Inner Classes - Object Programming

Question

I would like to understand Python classes and objects.

I am trying and struggling to get the output results from inner-class, Features.

class Person:
    def __init__(self):
        pass

    def first_name(self, first_name ):
        self.first_name = first_name
        return self.first_name

    def middle_name(self, middle_name):
        self.middle_name = middle_name

    def last_name(self, last_name):
        self.last_name = last_name
        return self.last_name

    class Features:
        def __init__(self):
            pass
        def color(self, color):
            self.color = color
            return self.color

x = Person()
print(x.last_name('Jimmy'))

print(x.Features.color('Brown'))

Instead I get this error:

TypeError: Person.Features.color() missing 1 required positional argument: 'color'

How can I do this correctly?

Answer 1

Your inner class is another class definition, just like the outer one.

a_person = Person()
a_feature = Person.Features()

For using it, you need to define it.

x = Person()
print(x.last_name('Jimmy'))
y = x.Features() # Or just Person.Features()
print(y.color('Brown'))

And the reason for the error:

missing 1 required positional argument

It's because you're trying to call the color() function without initializing the Features class. This means that the self argument, which would refer to the initialized class that doesn't exist now, is not passed down to the color function.

So it's giving you the error because it takes your "Brown" as the self parameter and so nothing is given to the color parameter; hence the:

Person.Features.color() missing 1 required positional argument: 'color'

Answer 2

I would not personally nest classes like this, but if you want to do that for some reason, this is a first step forward. The key here is that as part of the __init__() of Person, we __init__() their Features.

class Person:
    class Features:
        def __init__(self, color=None):
            self.color = color

    def __init__(self, first, middle, last):
        self.first_name = first
        self.middle_name = middle
        self.last_name = last
        self.features = Person.Features()

    def __str__(self):
        return f"{self.last_name}, {self.first_name}\n\tHair Color: {self.features.color}"

person = Person("Jane", "Mary", "Doe")
person.first_name="Sara"
person.features.color = "Red"
print(person)

That should give you:

Doe, Sara
        Hair Color: Red

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