[Qt-interest] QHash vs python dictionary

[Andre Somers]

On 25-5-2010 15:07, M. Bashir Al-Noimi wrote:
> Hi
>
> On 25/05/2010 11:16 ص, Andre Somers wrote:
>> On 25-5-2010 11:59, M. Bashir Al-Noimi wrote:
>>>
>>> Hi All,
>>>
>>> Currently I'm learning python for web developing. During my study I 
>>> leaned about python dictionary 
>>> <http://en.wikibooks.org/wiki/Python_Programming/Dictionaries> which 
>>> is very flexible data structure where C++ missed it, but I found 
>>> that QHash (and QMap) class is similar to it, is it true?
>>>
>>>
>>> On another side, python dictionary defines dynamic dimension 
>>> (infinite child dictionaries or lists) of data where QHash can't 
>>> (it's C++ template) so I'm wondering is there any Qt class can deal 
>>> with dynamic dimension of dictionary?
>>>
>>>
>>
>> Well, you can, actually. If you use QVariantHash (a typedef for 
>> QHash<QVariant>), you can store basically anything in your hash, 
>> including another QVariantHash. That would allow you the recursion 
>> you're after, at the price of dealing with QVariants. Of course you 
>> can also use other types than QVariantHash of course, if you register 
>> them for usage with QVariant.
> I can't expand QVariantHash by width at runtime because it's a C++ 
> templatewhere in python I can expand the dictionary in two dimensions 
> during insert process without any problem (just like making a tree).
In that case, I think that I misunderstood what you want to achieve, and 
so did Sean, I guess. I am not familiar with Python, so it is hard to 
imagine what the dimensionality you are talking about is all about. 
Could you give a simple code example?

If you want to add a second (third, fourth...) index to a hash, like you 
can with C arrays ( a[1][3] ), please note that this is really 
equivalent if a bit more elegant than what I described above. It does 
not matter if you store the "second-dimension" array/hash/map inside the 
first, or if the data structure really is a multi-dimensial beast. That 
is just syntactic sugar, and if you insist, you can make a simple 
wrapper class around the Qt container classes to make this work.

But perhaps you first need to make clear what is is exaclty that you 
want to achieve.

André


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