How to convert list of tuples into a single list of unique values ?

[Paul Rubin]

pekka niiranen <krissepu at vip.fi> writes:
> I have a list of equal size tuples, but a tuple may contain empty values:
> 
> t = [ ( a,b,c), (d, ,f) (b,a,j) ]
> 
> How can I convert it into a single list of unique values:
> 
> l = [a,b,c,d,f,j]
> 
> No lambdas, please

I don't think (d, ,f) is syntactically valid.  Other than that,
is something wrong with 
   import operator
   l = operator.add(*t)