Finding the instance reference of an object
joe at strout.net
Mon Nov 3 23:27:01 CET 2008
On Nov 3, 2008, at 2:36 PM, Aaron Brady wrote:
>> Then please write the Python equivalent of the "Swap" methods shown
>> <http://www.strout.net/info/coding/valref/> (or at <http://javadude.com/articles/passbyvalue.htm
>> >, for that matter).
>> And no fair wrapping the two parameters up in an object or using
>> packing/unpacking -- the point is to demonstrate that you can change
>> the two parameters themselves, not some object that contains them or
>> return them a different order.
> Python can do the swap operation on mutable types, for example.
That's in the "no fair" category. C can do a swap operation on
mutable types, too, though it also has only pass-by-value. Same for
Java, or for REALbasic or VB.NET using "ByVal" mode. The fact that
you can mutate mutable types has absolutely nothing to do with whether
the parameter was passed by reference or value. If was by reference,
you can change it (the parameter itself, not something the parameter
may refer to). If it's by value, you can't.
In Python, you can't. That's because parameters are passed by value.
> By-Value and By-Reference are not the only passing methods. True or
True, but the others are rarely used and don't apply to any of the
languages we've been discussing.
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