[Gnuplot-py-users] can't set date format, is that a bug?

Hi
I use gnuplot-py ,load a file to draw a graph:

Code:
import Gnuplot, Gnuplot.funcutils

g = Gnuplot.Gnuplot(debug=1)
g.title('a example') # (optional)
g('set timefmt "%Y%m%d"')
g('set xlabel "Date"')
g('set format x "%Y%m%d"') #---------------- bug?
g('set ylabel "JobNum"')
g('set xtics rotate')
g('set terminal png font "fonts/msyh.ttf" 12') # add !
g('set output \'graph_1.png\'') # add!
filename='hadoop.data'
thefile1 = Gnuplot.File(filename, using = (1,2), with_='lines')
g.plot(thefile1)

the data file's 1st column is date string.
It execute as this:
gnuplot> set terminal x11
gnuplot> set title "a example"
gnuplot> set timefmt "%Y%m%d"
gnuplot> set xlabel "Date"
gnuplot> set format x "%Y%m%d"
gnuplot> set ylabel "JobNum"
gnuplot> set xtics rotate
gnuplot> set terminal png font "fonts/msyh.ttf" 12
gnuplot> set output 'graph_1.png'
gnuplot> plot "hadoop.data" using 1:2 with lines

gnuplot: unable to open display ''
gnuplot: X11 aborted.
         line 0: Bad format character


the graph output is empty, but I execute it ok in gnuplot.

So is that a bug? Or how to set the output's format as date.


Thanks!