Python inheritance from lists [duplicate]

Question

I just started learning Python, and created the following class, that inherits from list:

class Person(list):
    def __init__(self, a_name, a_dob=None, a_books=[]):
        #person initialization code
        list.__init__(a_books)
        self.name = a_name
        self.dob = a_dob

However, there are three things I don't understand:

This line list.__init__(a_books), doesn't actually initialize my instance's list of books.
I am supposed, according to the book, write list.__init__([]) instead. Why is this step necessary.
Why is there no reference to self in list.__init__([])? How does Python know?

For a practical system you probably want list to be an attribute of Person rather then inherit from list. — Penguin Brian
– Penguin Brian, Commented Jan 27, 2016 at 1:04

user764357 · Accepted Answer · 2016-01-27 01:00:09Z

1

You need to make a super call to instantiate the object using the parents __init__ method first:

class Person(list):
    def __init__(self, a_name, a_dob=None, a_books=[]):
        #person initialization code
        super(Person, self).__init__(a_books)
        self.name = a_name
        self.dob = a_dob

print Person('bob',a_books=['how to bob'])

Gives the output:

['how to bob']

Because list has a __str__ method.

answered Jan 27, 2016 at 1:00

user764357

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