Re: lbc ListBox item sorting
- From: Alex Hall <mehgcap@xxxxxxxxx>
- To: programmingblind@xxxxxxxxxxxxx
- Date: Sat, 18 Jun 2011 22:33:24 -0400
You are right; I should have realized it. In fact, I should have
realized what the problem was when I saw the ordered dictionary
dependency in the PYLbc documentation (it is developed on python2.5).
I never thought of a dict as not caring about order like a list does,
but your explanation of it being simply a hash table makes sense (I
realize it is not intended as a full explanation and that there is
much reading to be found, but I do know what a hash table/associative
array is and its basic mechanism).
My first question stands, though, regarding a ListBox item's
"ClientData" value (and I have tried to find an answer to this one and
can only find a reference to sorting items, which is only possible
within the control... nothing detailed.) Looking at the AddListbox I
see that the ClientData is set to an integer i, where i goes from 0 to
the number of list items minus 1. Oddly, the "values" parameter of the
method is never used in the method itself, so I am unclear as to just
why it exists at all in the method.
On 6/18/11, Q <q@xxxxxxxxxxxxxxxxxx> wrote:
> Alex,
> May I recommend actually reading about the basic Python data types
> before attempting to create even simple applications?
> In particular, you should be aware that a dictionary is an inherently
> unordered type, as the underlying datastructure, namely a hash table, is
> unordered.
> The point of such a structure is for associating a key with a value. If
> you need to preserve ordering, either use an ordered dict (a Python 2.7+
> feature), or perhaps an alist-like sequence of tuples.
> You can also pull the keys out of a dictionary and sort them for use in
> a list box, something akin to
> lb = wx.ListBox(parent=self, value=sorted(some_dict)) #Note that this is
> taking advantage of the fact that iterating dicts gives their keys.
> But in all seriousness, please do go study the basics before hitting the
> list with a question like this.
> Q
>
>
>
>
> On 6/18/2011 9:17 PM, Alex Hall wrote:
>> Hi all,
>> When I use a ListBox, I see that I can give it a names list and a
>> values list. I understand that names are what is shown to the user,
>> but what do values do? They do not seem to be used in the AddListBox
>> method at all.
>>
>> A second question goes along with this: when I pass a list to be the
>> names list in a ListBox, all is well. When I pass a dictionary,
>> though, all my items suddenly get out of order. For example, if I pass
>> ["apple", "banana", "orange"] as the names list in the AddListBox
>> method, the items appear in that order. When I instead do this:
>> items={
>> "apples":"red",
>> "bananas":"yellow",
>> "oranges":"orange"
>> }
>> and then add to my dialog:
>> dlg.AddListBox(label="fruit", names=items.keys())
>> I get a list with the three fruits out of order, appearing as "apples,
>> oranges, bananas" in the list instead. I imagine this is a python
>> problem in the keys() method of the dictionary, but I cannot imagine
>> why it would do it at all. How do I get around it so that items appear
>> in the same order as they do in my dictionary? Thanks!
>>
>>
>
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--
Have a great day,
Alex (msg sent from GMail website)
mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap
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