[Tutor] reading configuration file

[Eur van Andel]

On Tue, 11 Nov 2003 13:28:48 +0000, Gonçalo Rodrigues <op73418 at mail.telepac.pt>
wrote:

>>Or do I have to invoke config[...] ? 
>>Do the elements of the dictionary become global variables?
>
>You have to use the config dictionary.
>
>>
>>Somehow the purpose of a dictionary eludes me. 
>
>There are 2 main problems with your approach.
>
>- You are polluting the global namespace with a lot of variables.
Yes, that is my FORTRAN heritage. Sorry. 

>Since they are all related isn't it better to put then all together?
Yes. 

>And now you can do other things. For example, write a report based on
>the config dictionary, e.g. something like
>
>>>> DEFAULTDICT = {"CO2_soll": 81}
>>>> lst = ["The config dictionary."]
>>>> for key, value in DEFAULTDICT.iteritems():
>... 	lst.append("%s = %s" % (key, value))
>... 	
>>>> print "\n".join(lst)
>The config dictionary.
>CO2_soll = 81
>
>Now try to do that with global variables.
You are right. 

>- Global variables are almost always BAD. In your example they were
>BAD because they got tightly coupled with the parse function. A
>function should be like a black box: it receives input via the
>arguments it receives, it gives output via return values. There should
>be no more interaction with its environment. By using global variables
I see that now too. I was used to globals. Sometimes, with not too many globals
it is easier, like in a microcontroller. 

>as you did you made the parse function dependent on its environment -
>a recipe for disaster. By avoiding global variables and having a
>dictionary as a return value we have made our function like a black
>box - no side effects on the surrounding environment.
>
>Any more question just holler,
>G. Rodrigues
>
>P.S: In the future send emails *also* to the Tutor list. That way all
>the participants can chime in and, hopefully, learn something.
I replied. I see now that replying doesn't work on the tutor mailing list. Why?

--
Ir. E.E. van Andel, Fine Wire Heat Exchangers, Fiwihex B.V. www.fiwihex.com
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