# newbie question about dictionnary ?

johnagianis johnagianis at yahoo.com
Fri Sep 5 15:07:07 CEST 2003

```"Sophie Alléon" <alleon at club-internet.fr> wrote in message news:<3f582f90\$0\$20952\$7a628cd7 at news.club-internet.fr>...
> Hi,
>
> CONTEXT
> I do numerical simulation for which I have to process mesh. A mesh is made
> of
> triangle which are made of points.
> I want from this information to create edges and build triangle from edges
> rather
> than from points.
>
> PROBLEM
> An edge is shared by possibly more than one triangle.
>
> ALGORITHM
>
> have a triangle class  (made of 3 edges)
> have an edge   class   (made of 2 points and embeding a triangle list (those
> connected to the edge)
>
> for each triangle construct its edges but I have to check if the edge
>
> for doing this I thought the dictionary was excellent but the key is a
> string while I want it
> to be the 2 points forming the edge ? How to do it ?
>
> Have you a better idea ?
>
> Thanks
>
> Guillaume

Dictionary keys are not necessarily strings. It can be even class
instances!! You can have the following:

class edge:
def __init__(self,x,y):
self.a=x
self.b=y
def ...
....

pointA=(3,1)
pointB=(5,2)
edgeA=edge(pointA,pointB)

triangle={}

triangle[edgeA]=something

Well i think that a list would be ok. The use of a dictionary is for
making a relation (key->value).In this case i dont know what the value
could be.

John

```