[Tutor] How does it work?

[Patty]

----- Original Message ----- 
From: "Patty" <patty at cruzio.com>
To: "Alan Gauld" <alan.gauld at btinternet.com>
Sent: Monday, January 03, 2011 9:05 AM
Subject: Re: [Tutor] How does it work?


> Hi Folks - I read this code and tried to parse it as a pop quiz for myself 
> ;) and have a question, maybe 2 clarifications,  below:
>
> ----- Original Message ----- 
> From: "Alan Gauld" <alan.gauld at btinternet.com>
> To: <tutor at python.org>
> Sent: Monday, January 03, 2011 8:09 AM
> Subject: Re: [Tutor] How does it work?
>
>
>> "Neo Vector" <neo_vector at yahoo.com> wrote
>>> Could you explain me how does it work, pls?
>>> ==============================
>>>>>>r = ''
>>
>> r is an empty string
>>
>>>>>>for c in 'abcd':
>>
>> c takes the value of each letter in turn
>>
>>>            r = c + r
>
> When I first looked at this - I thought that the variable 'c' would have 
> had to be initialized
> first earlier in the program.  And I thought that the programmer would 
> input a single char or a single space.   I wasn't thinking counting 
> variable for some reason.  So is 'for c in', one or more of key words that 
> Python understands that a loop is here and to actually trigger counting in 
> a loop? Does it start with a 1 or 0 internally to do this?
>
> I also realized a mistake I may have made - maybe I confused 'for c in' 
> with 'while c in'.
>
> r=''
> c="d"
> while c in 'abcd':
>   r=c+r
>
>    Or
>
> r=''
> c="d"
> while c in ['a', 'b', 'c', 'd']:
>   r=c+r
>
> Also for myself I think I would have used different descriptive names for 
> variables so that would have been less likely to throw myself off.  And 
> also doing this fast to see if I have learned.
>
> I really feel comfortable with Python now after six months and my small 
> application is completed and looks really good.   I don't know how I would 
> have been able to make the simplest, smallest GUI part of my application - 
> using Tkinter and PIL- fast without the references and explanations of 
> Wayne Werner and Alan -  Thanks to those on the list who are so helpful!
>
> Patty
>
>
>>
>> strings can be added such that the result is the concatenation of the two 
>> strings. So in this case:
>> r becomes the sum of its old value and the current value of c
>>
>> repeat for the next value of c.
>>
>> If that doesn't help then tell us which bit(s) of it you don't 
>> understand.
>>
>> HTH,
>>
>> -- 
>> Alan Gauld
>> Author of the Learn to Program web site
>> http://www.alan-g.me.uk/
>>
>>
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>