Rendering images/maps from Postgresql/PostGIS Database

Hi everyone!

I convert .osm - data into pgsql-database.

When I try to render images from these databases/tables.

I use Python version 2.7.2 with Mapnik-2.0.1rc0.

My .py:

#!/usr/bin/python

import mapnik
from mapnik import Layer, PostGIS
from datetime import datetime, timedelta
import sys, os

def render_image(start_time,end_time):

    ll = (30.708,-27.414,32.179,-25.652)
    prj = mapnik.Projection("+proj=latlong +datum=WGS84")
    c0 = prj.forward(mapnik.Coord(ll[0],ll[1]))
    c1 = prj.forward(mapnik.Coord(ll[2],ll[3]))

z = 3
imgx = 336 * z
imgy = 450 * z

m = mapnik.Map(imgx,imgy)
#mapnik.load_map(m,"some_kind_of_stylesheet.xml")

db_params = dict(
  dbname = 'gis',
  user = 'Hein',
  password = '1234',
  host = 'localhost',
  port = 5432,
  estimate_extent = False,
  extent = "3390650.221286806, -3163145.87245787, 3609898.596229789, -2956043.104540316"
)

lyr = Layer('points',"+init=epsg:900913")
###db_params['table'] = '(planet_osm_line,planet_osm_point,planet_osm_polygon,planet_osm_roads)'
db_params['table'] = 'planet_osm_point'
lyr.datasource = PostGIS(**db_params)
lyr.styles.append('points')
m.layers.append(lyr)

if hasattr(mapnik,'mapnik_version') and mapnik.mapnik_version() >= 800:
    bbox = mapnik.Box2d(c0.x,c0.y,c1.x,c1.y)
else:
    bbox = mapnik.Envelope(c0.x,c0.y,c1.x,c1.y)
m.zoom_to_box(bbox)
im = mapnik.Image(imgx,imgy)
mapnik.render(m, im)
view = im.view(0,0,imgx,imgy) # x,y,width,height
view.save("map.png",'png')

if __name__ == "__main__":
    cur_time = datetime(2010,8,10,0,0,0)
    end_time = datetime(2010,12,6,23,59,59)
    delta = timedelta(minutes=+30)
    while cur_time < end_time:
        render_image(cur_time.isoformat(), (cur_time+delta).isoformat())
        cur_time = cur_time + delta

I got this file from example-code and modified it. But there are some lines, where I don't know, what they mean and if they are useful.

What kind of XML-stylesheet must I use? Where can I get sample XML-code, that I can use?

I would be very happy if anyone could help me. Thank you!

Greets, Matze