[SciPy-User] Extracting common triplet from coordinate lists

[Borís BURLE]

Dear all,

I have three set of Cartesian coordinates and I would like to extract 
the positions that are identical in the three sets. Here is a toy example:

x1 =  [1,2,3,4]
y1 =  [4,3,2,1]
z1 =  [3,4,1,2]

x2 =  [7,1,2,3]
y2 =  [5,4,3,2]
z2 =  [6,3,2,1]

x3 =  [7,6,1,3]
y3 =  [5,4,4,2]
z3 =  [6,9,3,1]

In this example, I would like to extract the triplets (1,4,3) and 
(3,2,1) since they are common to the three sets. As you can notice, the 
position of the common triplet is variable. In this example, data are in 
list, but any code working  on arrays would be ok for me too !!

    Do you have any idea on how to do that?
       Thanks in advance,
             Boris

-- 
Borís BURLE
Laboratoire de Neurobiologie de la Cognition
CNRS et Université de Provence
tel: (+33) 4 88 57 68 79
fax: (+33) 4 88 57 68 72
web page:  http://www.up.univ-mrs.fr/lnc/ACT/act-fr.html