[Tutor] Bug in python, or is it just 3am

[Liam Clarke]

Hi Ryan,

I see what confused you; the

"
>>> number + 1
6
>>> print number
5
"

part. Yeah, it's only evaluating the the first one. So you're asking
it "What's number + 1"?
Whereas,

>>> number = number + 1

or

>>> number += 1

Is saying "Make number equal number plus 1"

Ha, it's all a learning experience.

Regards,

Liam Clarke

On 4/21/06, Alan Gauld <alan.gauld at freenet.co.uk> wrote:
> > But when i use a number = number + 1
> > right after the value stays the same,
>
> I'm not sure what you mean by that.
>
> > Now i thought that number = number + 1 just wasn't
> > vailed in python untill i tried it again and it
> > worked,
>
> variable = variable + 1
>
> is perfectly valid. It is not the normal math meaning of an equation
> however, it is an assignment statement. In a language like Smalltalk
> or Pascal they use a different symbol (:=) for assignment which
> is IMHO A Good Thing(TM)  And they traditionally read that
> symbol as "becomes", thus:
>
> variable := variable + 1
>
> is read: "variable becomes variable plus one"
>
> What it means is that variable takes on the previous value
> of variable plus one. So if it starts as 42 it ends as 43
>
> This is such a common thing to do that Python actually
> has a shorthand for it:
>
> variable += 1
>
> And after all that, I've just realised that I don't discuss this
> at all in my tutorial so I need to add an explanation this weekend.
> So thanks for asking the question! :-)
>
> HTH,
>
> Alan G
> Author of the learn to program web tutor
> http://www.freenetpages.co.uk/hp/alan.gauld
>
>
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