[Tutor] global variables/constants versus volatile variables/constants

[ALAN GAULD]

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Alan Gauld
Author of the Learn To Program website
http://www.alan-g.me.uk/

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>________________________________
> From: diliup gabadamudalige <diliupg at gmail.com>
>To: Alan Gauld <alan.gauld at btinternet.com> 
>Sent: Friday, 13 June 2014, 9:32
>Subject: Re: [Tutor] global variables/constants versus volatile variables/constants
> 
>
>
>thanks Alan!
>
>in the program that i am writing i used a class called variables and declare all variables i use in the program in the def __init__ section.
>so all variables which otherwise would have to be declared as global so that they can be modified  by other functions are in a class. 
>Is this ok?
>The strings, lists and dictionaries which are not read only are used as locals in functions and classes.
>If there is a string, list or dict. which is used in several functions is it better to use a global or several locals?
>
>
>
>On Fri, Jun 13, 2014 at 1:25 PM, Alan Gauld <alan.gauld at btinternet.com> wrote:
>
>On 13/06/14 08:21, diliup gabadamudalige wrote:
>>
>>
>>In my code there are many dictionaries and lists which are used in
>>>various functions. Is it better/pythonic/efficient to have these inside
>>>the function itself or declared at the beginning of the program in which
>>>case they will be global?
>>>
>>
If you are sharing a set of data structures between several functions thats often a sign they should be in a class. The data then becomes the class instance attributes and the functions become the methods.
>>
>>
>>
>>global constants and variable have memory allocated to them but when
>>>declared inside a function are created on the fly, used and discarded.
>>>
>>
That's not usually the main issue when deciding for global/local.
>>Its more about the maintainability of the code and the over
>>use of side effects which makes the code difficult to read.
>>If the data is read only then things are not so bad and globals
>>can be an OK solution.
>>
>>hth
>>-- 
>>Alan G
>>Author of the Learn to Program web site
>>http://www.alan-g.me.uk/
>>http://www.flickr.com/photos/alangauldphotos
>>
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>
>
>
>-- 
>
>Diliup Gabadamudalige
>
>http://www.diliupg.com
>http://soft.diliupg.com/
>
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