[Tutor] Inherit from int?

[wesley chun]

> I'm stumped.  This silly bit of code doesn't work.  I expect the
> output to be 8, not 18.  What am I missing?
>
> class Under10(int):
>     def __init__(self, number):
>         number %= 10
>         int.__init__(self, number)

marilyn,

i agree with most of the earlier replies... you need to use __new__()
instead of __init__() in order to "tweak" the original value before
the instance of the immutable object is created. once it's "frozen,"
you're stuck.  note that __new__() is a class method, so you'll need a
variable for the class (instead of self for the instance).

also recall that __init__() is (the 1st method) called *after* an
instance has been created, which for you, would be too late.  in
practice, i don't think __init__() is ever used for deriving from
immutable types.  does anyone have a counterexample?

(since i know you've been reading Core Python, you can take a look at
my example of subclassing an immutable type on p.552.)  :-)

cheers,
-- wesley
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
"Core Python Programming", Prentice Hall, (c)2007,2001
    http://corepython.com

wesley.j.chun :: wescpy-at-gmail.com
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cyberweb.consulting : silicon valley, ca
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