Your function is f; f(x) is the function evaluated at a point, x. If you want to target f as the the replacement you have to define f separate from the "(X)" part:
>>> f=Function('theta') >>> f(x) theta(x) >>> _.subs(f, sin) sin(x) -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sy...@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.