from mapnik import Map, Layer
proj4 = '+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378137 +b=6378137 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs'
m = Map(256,256,proj4)
lyr = Layer('Name',proj4)