add example for Python with vector-style variable

examples/python/in.python.wrap

@@ -1,9 +1,9 @@
 # 3d Lennard-Jones melt with equal- and atom-style variables which
 #   use a Python function wrapper in their formulas
 
-variable        x index 5
-variable        y index 5
-variable        z index 5
+variable        x index 3
+variable        y index 3
+variable        z index 3
 
 units           lj
 atom_style      atomic
@@ -24,21 +24,37 @@ neigh_modify    delay 0 every 20 check no
 
 fix             1 all nve
 
+# define Python truncate() function
+
 variable        foo python truncate
 python          truncate return v_foo input 1 iv_arg format fi here """
 def truncate(x):
   return int(x)
 """
 
+# use in equal-style variable
+
 variable        scalar equal py_foo(4.5)
 print           "TRUNCATE ${scalar}"
 
+# use in atom-style variable
+# examine dump file to see truncated xyz coords of each atom
+
 variable        xtrunc atom py_foo(x)
 variable        ytrunc atom py_foo(y)
 variable        ztrunc atom py_foo(z)
 
-# examine dump file to see truncated xyz coords of each atom
-
 dump            1 all custom 100 tmp.dump id x y z v_xtrunc v_ytrunc v_ztrunc
 
+# use in vector-style variable
+
+compute         ke all temp
+variable        ke vector c_ke
+variable        ketrunc vector py_foo(v_ke)
+thermo_style    custom step temp epair v_ketrunc[*6]
+
 run             100
+
+print           "KE TENSOR ${ketrunc}"
+
+