Moving list entries from one list to another

[JB]

Bengt Richter wrote:

> On Sat, 13 Jul 2002 22:32:32 +0200, JB
> <jblazi at hotmail.com> wrote:
> [...]
>>
>>f will be *slow*. The list entries are tuples and the
>>tuple entries are strings. Then f is "in" for strings,
>>that is it checks, if one string contains another one.
>>What I want to implement, is a list view with incr4emental
>>search. There
> What kind of incremental search? Just matching leading
> characters? Or matching additional words anywhere? Or
> arbitrary word fragments? Or?
>  
>>will be up to 250000 entrie in the list view at the moment
>>(for example all headers of the news group
>>alt.binaries.mp3.classical) and this number is going to
>>increase in the  future as news servers become bigger and
>>bigger. I thought that when f is slow, then at least the
>>merging should be as fast as possible.
> This sounds like the data changes fairly infrequently
> compared to how often it's searched. Would a costly
> indexing job run infrequently be worth while if it paid
> off in search speed?
> 
> There are probably better ways to generate a selection
> than brute scanning of python lists with strings, but just
> to get the requirements down, does this do the kind of
> incremental search you are interested in?
> --
>  >>> class IncSrch(object):
>  ...     def __init__(self, master_list):
>  ...         self.master = master_list
>  ...         self.curr = []
>  ...     def new_search(self, patt):
>  ...         self.curr = [x for x in self.master if
>  x[1].find(patt)!= -1]
>  ...     def inc_search(self, patt):
>  ...         self.curr = [x for x in self.curr if
>  x[1].find(patt)!= -1]
>  ...     def __repr__(self):
>  ...         return '\n'.join([`x` for x in self.curr])
>  ...
> 
> Here we just generate a list of example tuples with ids
> and random-suffix strings:
>  >>> import random
>  >>> r = random.Random()
>  >>> master1 = [(i,'item_%s%s' %
>  >>> (r.choice('ABCD'),r.choice('XYZW'))) for i in
>  >>> xrange(10)] master1
>  [(0, 'item_AZ'), (1, 'item_BX'), (2, 'item_BY'), (3,
>  ['item_BZ'), (4, 'item_AZ'), (5, 'item
>  _BW'), (6, 'item_BW'), (7, 'item_DY'), (8, 'item_BY'),
>  (9, 'item_CY')]
> 
> (Is this like your data? Or how does it differ?)

This is ok. The real data are much longer strings, but it is 
ok.

> 
> Here we initialize a search object with a master starting
> list and nothing selected
>  >>> is1 = IncSrch(master1)
>  >>> is1
> 
>  >>> `is1`
>  ''
> I.e., there is nothing selected to the curr list yet.
> 
> Here we do a first search based on containing substring
> 'D':
>  >>> is1.new_search('D')
> Just typing the name calls repr to print the current state
> of the search object:
>  >>> is1
>  (7, 'item_DY')
> 
> That wasn't much to do a secondary search on, so we do a
> new search on the master list for 'B':
>  >>> is1.new_search('B')
>  >>> is1
>  (1, 'item_BX')
>  (2, 'item_BY')
>  (3, 'item_BZ')
>  (5, 'item_BW')
>  (6, 'item_BW')
>  (8, 'item_BY')
> 
> That got a few, so we incrementally search for 'Y':
>  >>> is1.inc_search('Y')
>  >>> is1
>  (2, 'item_BY')
>  (8, 'item_BY')
> 
> And so forth. Is that the kind of thing you want to do?

Yes.

> I presume you have to pass a list of items in some form to
> the display widget, and that you will not want to pass
> more than say MAX_FOR_WIDGET items for a reasonable
> scrolling display, and you may(??) need the items as a
> list of strings, not tuples, so you might want to add a
> first_for_widget() and next_for_widget() method to the
> class as part of the definition (but I'll do it separately
> here since I have some state above to use):

Of course, only 40 or so lines can be displayed at the same 
time. It plays no rôle if I pass list or tuples of strings.

> If you will comment on what this simple class does and
> doesn't do that you need functionally, that will establish
> unambiguous requirements. Then we can make it fast one way
> or another.

That is exactly. what I want. I do not quite understand in 
your soulution, what you do, when the search string is 
shortened by the user. Let us assume, he had typed in "Mo" 
(for Mozart) but then he decides he is looking for "Me" 
(another composer). So he deletes the "o". What happens 
then? This is, why I thought, I should need two lists.

-- 
Janos Blazi


-----------== Posted via Newsfeed.Com - Uncensored Usenet News ==----------
   http://www.newsfeed.com       The #1 Newsgroup Service in the World!
-----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =-----