Hi, I’ve been using matplotlib for about a week now and am exceedingly confused by all the class hierarchies and stuff.


I’m trying to draw an arc and some other polygons and render them to either GTK or postscript.  I’m running Python 2.4 with Idle and XP


I can successfully do the following:

1.  Using the matlab-ish commands, I can create a figure, polygons, circles, and use add_patch() to add these shapes to the figure. 

2.  I can direct it to GTK or PS with the matplotlib.use command.  I can print out the resulting PS file just fine, and the plot shows up on the screen with GTK just fine.


The problem is I want to draw arcs.  I don’t see an Arc() command at the same level as Polygon and Circle.  The only place I see an arc is with the renderer classes.


I tried extracting the current renderer from the figure and axis (via the _cachedRenderer attribute), but those don’t seem to be assigned until I do a savefig() or a show(), but obviously I want the renderer before any show()ing or savefig()ing.


So then I tried creating a RendererPS class directly (instead of RendererAgg as in the User’s Guide).  It seems to want a pswriter argument.  I looked around and saw that pswriter is expected to be some type of cString.StringIO or something, which seemed too low-level, and I figured I didn’t want to mess around any more.  I just want to draw a stupid arc.


Also, if I have a GTK figure, and then do show(), it plots a nice figure on the screen.  If I then close it, type show() again, my python window freezes up and I have to kill it with the process manager.


If anyone can shed some light on these problems I’d be much happier J