Continuation... here is a standalone python program that causes no error messages but does not do what I expect it to do: ----------------------------------------------- import re,rexec r = rexec.RExec() def dothis(r,ctag,content,otag): print content r.r_exec("""a="%s" """%content) return "eval to:%s "%r.r_eval('a') c='asdf' a=r'(?ims)<(py|que)>(.*?)</(\1)>' text="<py>do this</py><que>a</que>" print re.sub(a,dothis(r,r'\1',r'\2',r'\3'),text) ------------------------------------------------ The trouble is that \1, \2, \3 are like pointers, not the actual match while it is in the method dothis. So it does not process the content. BUT, it I use a compiled regular expression and rexp.sub(dothis,text) then it does work but I lose access to r (the restricted python environment) You could argue: why not put r inside the dothis function. Yes this would work but then I cannot have make use of previous python calculations within the same wikipage. Bruno