The Cost of Dynamism (was Re: Pyhon 2.x or 3.x, which is faster?)

[BartC]

On 14/03/2016 19:45, alister wrote:
> On Mon, 14 Mar 2016 14:43:22 +0000, BartC wrote:
>
>> On 13/03/2016 09:39, Steven D'Aprano wrote:
>>> On Sun, 13 Mar 2016 04:54 am, BartC wrote:
>>
>>>> Common sense tells you it is unlikely.
>>>
>>> Perhaps your common sense is different from other people's common
>>> sense. To me, and many other Python programmers, it's common sense that
>>> being able to replace functions or methods on the fly is a useful
>>> feature worth having. More on this below.
>>>
>>> Perhaps this is an example of the "Blub Paradox":
>>
>> Perhaps it's time to talk about something which many languages have, but
>> Python hasn't. Not as far as I know anyway.
>>
>> That's references to names (sometimes called pointers). So if I write:
>>
>>    a = 100 f(a)
>>
>> then function f gets passed the value that a refers to, or 100 in this
>> case. But how do you pass 'a' itself?

> Congratulations
> you have just proven that you have faild in your understanimg of python @
> stage 1 becuae you keep tying to us it a C
>
> try the following
>
> def test(x):
> 	print (id(x)
>
> a=100
> print (id(a))
> test(a)
> a="Oops i was an idiot"
> print (id(a))
> test(a)
>
> python always passes the object bound to a, not the value of a or a
> pointer to a

Yes, and? I colloquially used 'value' instead of 'object', 'id' or 
'reference'. The latter would added confusion as I'm talking about a 
different kind of reference. And if you get rid of 'id' in your code, 
you will get values displayed.

But how do you pass something that refers to a itself?

There are good reasons for wanting to do so. Try writing this function 
in Python:

def swap(a,b):
     b,a = a,b

x="one"
y="two"
swap(x,y)

print (x,y)

so that it displays "two" "one".

-- 
Bartc