Dealing with Lists

[stas poritskiy]

Steven,
i think you got on the right track with your proposal,
although i am not going after the "visual" represenatation that you were able to create, rather a structural one, i think this might work for me,
instead of printing, i could be using my commands to make elements (instances of API objects to create my groups inside the file)

but one question i might have is :

once i created first instance object which in my example is :
groups = intance.add_group(str(name))

how would i temporary preserve this name as a reference for the next iteration for the subroups?

On Tuesday, September 10, 2013 10:13:48 PM UTC-5, Steven D'Aprano wrote:
> On Wed, 11 Sep 2013 02:24:44 +0000, Dave Angel wrote:
> 
> 
> 
> > On 10/9/2013 22:14, Steven D'Aprano wrote:
> 
> > 
> 
> >> On Tue, 10 Sep 2013 14:08:45 -0700, stas poritskiy wrote:
> 
> >>
> 
> >>> Greetings to all!
> 
> >>> 
> 
> >>> i ran into a little logic problem and trying to figure it out.
> 
> >>> 
> 
> >>> my case is as follows:
> 
> >>> 
> 
> >>> i have a list of items each item represents a Group i need to create a
> 
> >>> set of nested groups, so, for example:
> 
> >>> 
> 
> >>> myGroups = ["head", "neck", "arms", "legs"]
> 
> >>
> 
> >>
> 
> >> What is the rule for grouping these items? Below, you suggest:
> 
> >>
> 
> >> head encloses neck
> 
> >> neck encloses arms
> 
> >> arms encloses legs
> 
> >>
> 
> >> which seems rather strange. But if it is *always* the case that each
> 
> >> item encloses the next item:
> 
> >>
> 
> >> def print_nested_list(alist):
> 
> >>     spaces = ' '*4
> 
> >>     for level, item in enumerate(alist):
> 
> >>         if level != 0:
> 
> >>             indent = spaces*(level-1) + '  '
> 
> >>             print (indent + '|_>'),  # note comma
> 
> >>         print item
> 
> >>
> 
> >>
> 
> >> which gives us this:
> 
> >>
> 
> >> py> print_nested_list(['head', 'neck', 'arms', 'legs']) head
> 
> >>   |_> neck
> 
> >>       |_> arms
> 
> >>           |_> legs
> 
> >>
> 
> >>
> 
> >> as requested.
> 
> >>
> 
> >>
> 
> >>
> 
> > Very nice.  But what I want to know is how did you know that Stan (the
> 
> > OP) wanted his printed output to be formatted that way?
> 
> 
> 
> I don't. Stan's email is unclear. But he does show an example:
> 
> 
> 
> [quote]
> 
> so, for example:
> 
> 
> 
> myGroups = ["head", "neck", "arms", "legs"]
> 
> 
> 
> i need to get them to be represented like this: (if you can imaging a
> 
> folder structure)
> 
> 
> 
> head
> 
>   |_> neck
> 
>         |_> arms
> 
>               |_>legs
> 
> 
> 
> and so on until i hit the last element.
> 
> [end quote]
> 
> 
> 
> 
> 
> so I just provided that.
> 
> 
> 
> > He said:
> 
> > 
> 
> >>>>>> i need to create a set of nested groups,
> 
> > and
> 
> >>>>>> store each of the first elements of a par, so I can reference to
> 
> >>>>>> them as to a parent of another group.
> 
> 
> 
> 
> 
> I have no idea what that means :-)
> 
> 
> 
> 
> 
> I *guess* that what Stan is actually looking for is something like a 
> 
> dictionary-based solution, not lists:
> 
> 
> 
> {'head': {'neck': {'arms': {}, 'legs': {}}}}
> 
> 
> 
> which gives:
> 
> 
> 
> head encloses neck
> 
> neck encloses arms and legs
> 
> arms enclose nothing
> 
> legs enclose nothing
> 
> 
> 
> 
> 
> or:
> 
> 
> 
> {'head': {'neck': {'arms': {'legs': {}}}}}
> 
> 
> 
> which gives:
> 
> 
> 
> head encloses neck
> 
> neck encloses arms
> 
> arms encloses legs
> 
> legs enclose nothing
> 
> 
> 
> 
> 
> but I can't really tell for sure. In this second case, using dicts, I 
> 
> might try something like this recursive solution:
> 
> 
> 
> 
> 
> def print_nested_dict(adict, level=0):
> 
>     if adict == {}:
> 
>         return
> 
>     for key, subdict in sorted(adict.items()):
> 
>         if level != 0:
> 
>             spaces = ' '*4
> 
>             indent = spaces*(level-1) + '  '
> 
>             print (indent + '|_>'),  # note comma
> 
>         if subdict == {}:
> 
>             print key
> 
>         else:
> 
>             print "%s:-" % key
> 
>             print_nested_dict(subdict, level+1)
> 
> 
> 
> 
> 
> Given:
> 
> 
> 
> d = {'head': {'neck': {'legs': {'toes': {}}, 'arms': {'thumbs': {}, 
> 
> 'fingers': {}}}}}
> 
> 
> 
> we can see this output:
> 
> 
> 
> py> print_nested_dict(d)
> 
> head:-
> 
>   |_> neck:-
> 
>       |_> arms:-
> 
>           |_> fingers
> 
>           |_> thumbs
> 
>       |_> legs:-
> 
>           |_> toes
> 
> 
> 
> 
> 
> 
> 
> 
> 
> -- 
> 
> Steven