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Date: Wed, 22 Aug 2012 16:31:08 -0500
From: Evan Driscoll <driscoll@cs.wisc.edu>
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To: lipska the kat <lipskathekat@yahoo.co.uk>
Subject: Re: Re: Objects in Python
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On 08/22/2012 02:45 PM, lipska the kat wrote:
> On 22/08/12 20:03, Evan Driscoll wrote:
>> Second, this concept isn't *so* unfamiliar to you. If I give you the
>> following Java code:
>>
>>    void foo(Object o) { ... }
>>
> looking at this method declaration I can see that the method takes an
> argument of type Object (and just FYI class Object is not abstract and
> you can do Object o =3D new Object()) and does not return a value.
> I know that for the lifetime of this JVM, whatever o turns out to be it=

> will always be an Object. I can't assign a primitive to o as ints chars=

> floats etc are certainly not Objects. There are certain invariants that=

> give me a warm and comfortable feeling inside.

I'm not saying it's nothing, but "can't assign a primitive" isn't much
of an invariant in the broad scheme of things when you can pass items as
diverse as lists, GUI buttons, files, etc. I would say it's more like if
you see 'int x' then *that* imposes a pretty big invariant, but passing
'Object' imposes almost nothing.

This is especially true considering the fact that you actually *can* say
'foo(4)' and Java will go and autobox the 4 into Integer(4) for you.

(BTW, this analogy suggests a way that's actually fairly useful for how
to look at Python coming from the Java perspective: Python just lacks
primitive types and things like integers are always boxed. Thus *all*
Python variables are essentially references.)

Evan


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