[Tutor] Object references and garbage collection confusion

[Brandon D]

>
> This is what was also confusing as well.  I assumed that python stored
> objects rather than simply assigning them.
>

On Tue, May 5, 2015 at 4:48 AM, Alan Gauld <alan.gauld at btinternet.com>
wrote:

> On 05/05/15 05:29, Brandon D wrote:
>
>> Hello tutors,
>>
>> I'm having trouble understanding, as well as visualizing, how object
>> references work in the following situation.  For demonstration purposes I
>> will keep it at the most rudimentary level:
>>
>> x = 10
>> x = x ** x
>>
>
> Its good to use a simple example but in this case your
> example bears no relation to your comments below!
>
>
>> If my knowledge serves me correctly, Python destroys the value once
>> reassigned.
>>
>
> Eventually.
> Or more accurately Python marks the object for deletion
> once all references to the object have been lost. Remember
> variables in Python are not storage locations, they are
> names attached to objects. When there are no more names
> attached to an object it can be deleted. But that does
> not necessarily happen immediately, Python gets around
> to it when it has the time.
>
>  So, how does x = x +  1 work if it's destroyed before it can
>> be referenced?
>>
>
> Its not. This says assign x to the object on the right.
> So it has to work out what "the object on the right" is
> before it can stick the label x onto the result.
>
>  The only solution I came up with is that the two operands
>> are evaluated before storing it in the variable, consequently
>>
> > replacing the original value of 0.
>
> Remember, its the name that moves, not the objects. Python
> doesn't store the objects in the variables, it assigns
> the variable names to the objects. There is a big difference.
>
> HTH
> --
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> http://www.amazon.com/author/alan_gauld
> Follow my photo-blog on Flickr at:
> http://www.flickr.com/photos/alangauldphotos
>
>
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