> Dictionaries are only pairs of data. I assume a list can be one of
> those elements, but I couldn't figure out how to make it work in the
> structure I presented.
Yes, the object that is stored can be anything. Thus
>>> numList = [1,2,3]
>>> chrList = ['1','2','3']
>>> numDict = {}
>>> numDict['asNum'] = numList
>>> numDict['asChr'] = chrList
>>> for item in numDict['asNum']: print item,
...
1 2 3
>>>
shows two lists being stored in a dictionary.
You can also store instances of classes or functions
or even the classes themselves!
> I wanted to make the methods flexible enough that I wouldn't have to
> edit every method if the module list ever changed. I guess I don't
> understand how a dictionary works in this situation.
I don;t understand what you don;t understand here. Can you
expand on why you don't think a dictionary would work?
>> Why not write constructors that take a list as a parameter.
>> The constructor can manage its own list and the higher
>> level constructor just passes in the appropriate list. That way
>> each class only needs to know about the data at the level
>> it is responsible for. So the Module class might look a bit like:
>>
>> class Module:
>> def __init__(self, name, componentlist):
>> self.components = {}
>> self.name = name
>> for component in componentlist:
>> self.components[component[0]] = Component(component)
>>
>> This implies that the component list is structured as a list of tuples.
>
> I originally had tuples, but you can't access individual elements.
What makes you think so?
>>> t = (1,2,3)
>>> print t[0]
1
>>>
The only thing you can't do is alter the data in the tuple - which is
exactly the behaviour you want if reading the tuple from a config file!
>>> I have object "db.mb". I have iterator "shortmod" with a value of
>>> "mb". Why can't I call "db.shortmod"?
>>
>> You can use db.getattr(shortmod)
>
> That doesn't work. It tells me "Database instance has no attribute
> 'getattr'".
Its actually a special method so needs the underscores __getattr__
and accessed via a function. I got my syntax muddled:
getattr(db, shortmod)
is how it should be written.
>> but I think its easier and clearer in this case to use:
>>
>> db.Modules[shortmod]
>
> If Modules is a class name, how am I able to call it like that?
Modules is a dictionary of Modules in the db object. I
should probably have used the example from my Module
class above:
myModule.components[compname]
> "AttributeError: Database instance has no attribute 'Modules'"
You will need to modify the definition of the database class
to have the Modules dictionary first! :-)
Alan G
Author of the learn to program web tutor
http://www.freenetpages.co.uk/hp/alan.gauld
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