from mapnik import Map, Layer
proj4 = '+proj=cass +lat_0=52.43725961111112 +lon_0=112.7288297222222 +x_0=0 +y_0=0 +ellps=bessel +datum=potsdam +units=m +no_defs'
m = Map(256,256,proj4)
lyr = Layer('Name',proj4)