Robert Dailey wrote: [but he top-posted, so he should consider himself smacked on the wrist] > On 8/16/07, *Steve Holden* <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > Robert Dailey wrote: > > So immutable objects cannot be modified directly? I guess this means > > integers are immutable and the act of assigning to one is a > completely > > new definition? > > Correct. A new value is bound to the name or item on the left-hand side > - remember, all variables are pointers to values, there's no way to > replace the value of a variable because of the automatic dereferencing. > And yes, immutable objects can't be modified. At all, period. Hence the > name. > > > So if I were to create a class called Integer and > give > > it a .set() method, this would allow me to create mutable > integers, and > > thus passing in an object of type class Integer would allow me to > modify > > the value from inside the function? > > > Well, the .set() method wouldn't be called automatically on an > assignment statement but yes, if you passed an Integer object into your > function and called its .set() method from inside then it should work. > > As long as you get your mutable integer implementation correct, of > course ;-). I'd suggest delegating everything except the .set() method > to the underlying integer value.
> Thanks Steve for your explanation. It was very helpful. I think I > understand it now. By the way, by the .set method I meant: > > class Integer: > def __init__( self, number=0 ): > self._int = number > > def set( self, number ): > self._int = number > > > # later on.... > > mutableInt = Integer( 5 ) > def change_me( var ): > var.set( 6 ) > > > Of course, I'd probably use overloaded operators in a more realized > example. > > Fair enough, but I was trying to point out that assignment isn't an operator so you won't be able to achieve what you want by assignment to a name local to the function. You could, of course, assign to a name local to the instance you passed in, but then there wouldn't be much point in using anything but a simple subclass of object (normally referred to as Bunch). regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://del.icio.us/steve.holden --------------- Asciimercial ------------------ Get on the web: Blog, lens and tag the Internet Many services currently offer free registration ----------- Thank You for Reading ------------- -- http://mail.python.org/mailman/listinfo/python-list
