custom command : how to append dynamically columns

I try to write a python command that generates results. My problem is, that I have "n" columns, and the name of them is might be different from line to line. I can't make it with the normal results.append/outputresult

    results.append({'_time' : time, '_raw' : output})   
    si.outputResults(results)

How could I do that, it there a way to append line by line, with the columns defined in variables ?

append["line1"]
    appendcol["_time"]=time
    appendcol[r]=rr
    appendcol[s]=ss
append["line2"]
    appendcol["_time"]=time
    appendcol[x]=xx
    appendcol[y]=yy