"Alex Companioni" <achom...@gmail.com> wrote
class Tomato(list):
def __init__(self, data):
list.__init__(self, data)
The list.__init__ method (if it is a method, I'm not clear on what
__init__ actually *is*) creates a list, right?
Not quite. __init__ (which is a method) is an initialiser not
a constructor(*). The list is already created when you call
init(). (Thats done by the __new__() class method)
l = Tomato([1,2,3])
will create a list l with the values [1,2,3], correct?
Correct. But the creation of the list is done in the
superclass __new__() not in the init. The assignment of
the data to the list is done by __init__()
(*)Although init is not really a construxctir it is usually treated
as one and often referred to as such by Python programmers.
Indeed I do the same in my tutorial. But technically new()
constructs the class, init initialises it.
<Aside nature=off-topic>
This is similar to Objective C which also has separate
constructor/initialiser functions namely alloc and init. So you
can create an ObjC object like
myObj = [ [MyClass alloc] init ]
But this is such a common combination that ObjC provides
the wrapper new:
myObj = [MyClass new]
Which is how ObjC programmer create classes 99% of the time!
</Aside>
HTH
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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