How would you go about computing special values of L-functions attached to modular form, twisted by a Dirichlet character?
there seems to be no package, although this should be one of the basic features that SAGE provides.
I'm not into modular forms, but you can get Dirichlet characters via
DirichletGroup
in Sage. Have you looked at http://sagemath.org/doc/reference/lfu... ? What did you try?