[Tutor] tree or link-list questions.

[mhysnm1964 at gmail.com]

Allan,

Once again, thanks for the help. I need to read more on OOPS it is all new
and that was my first attempt. I looked at nesting Dictionaries and it got
quite complex fast with the length of the strings and the path as you have
outlined. I have parked that structure style for now.

All these answers are really helping me to improve my programming knowledge
and narrowing my definition.

The reason why I am using the tree structure like a file system. Is I am
going to attempt to write some code to walk down the tree based upon certain
conditions which I am still working on. Based upon the test conditions will
determine how I move up and down the tree.

The high picture is I am trying to build a dynamic search functionality
based upon keywords in the text. Like a store name or organisation name. The
text has been cleaned up before applying it to the tree based upon text or
punctuation and digits that are not required. Such as receipt  numbers,
postcodes, braces, etc. This is mostly done. I am hoping the tree structure
will help in finishing the search capability. I will only know once I have
tried it. If not, then I will look for another method.

I am enjoying what I am doing because I am learning. I am pushing myself
beyond my normal level of skills. Playing in the dark as I say. LOL 

Sean 
-----Original Message-----
From: Tutor <tutor-bounces+mhysnm1964=gmail.com at python.org> On Behalf Of
Alan Gauld via Tutor
Sent: Wednesday, 26 June 2019 2:48 AM
To: tutor at python.org
Subject: Re: [Tutor] tree or link-list questions.

On 25/06/2019 13:24, mhysnm1964 at gmail.com wrote:
... the tree I am trying to create is:
> 
> *	A single root node
> *	A node can only have a single parent.
> *	A parent can have multiple children.
> *	Each node is unique.

A tree with multiple children (where multiple is more than 2) is entirely
possible but does make the code more complex.

Have you considered a binary tree where items go either left or right
depending on whether they are "greater than" or "less than" (for some
arbitrary definition of greater and less) than the parent node?
This is much simpler to code, and you will find lots of examples online.

------ monospace font needed -------
<pre>
Root
   the
      brown
         fox
         cow
         car
      yellow
         car
      green
         house
      quick
         brown
            fox
   yellow
      flowers
</pre>
------ end of monospace font -------

The immediate questions you must answer (because only you understand the
requirements) are:
1) How do you know which tree branch to navigate down?
For example you have two car nodes. If searching for car which is the
correct answer? Similarly for fox?

2) How do you know to go down an extra level. For example there are 4 nodes
below 'the' What determines whether a new node sits alongside the existing
nodes or at a level below.

3) Having decided you need to go a level lower how do you know which subnode
to go down? How do you insert the node car into the correct subnode of
the?(either brown or yellow)

It looks like you are doing this based on the textual context.
That means you insertion code has to be stateful since it must remember the
previous word inserted (or have access to the original data). That gets
complicated really quickly.

Similarly, when you try to retrieve the data how do yu know which node to
fetch. For example if I search for fox? Surely you will need to provide the
full 'path' to fox topick the right one? But if you know the path why search
a tree?

In that case nested dictionaries would seem a better solution?
Something like(missing all the quotes!):

data = {
   the: [
      {brown: [
         {fox:[]},
         {cow:[]},
         {car:[]},
         ]},
      {yellow: [
         {car: []}
         ]},
      {green: [
         {house: []}
         ]},
      {quick: [
         {brown: [
             {fox: []}
             ]},
         ]},
       ]},
   {yellow: [
      {flowers: []}
      ]}
   ]}

Then you can access the appropriate path:

myFox = data[the][quick][brown][fox]

Just a thought. Since I don't really know how you intend to use this I'm not
sure if that would work for you.


--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos


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