from mapnik import Map, Layer
proj4 = '+proj=tmerc +lat_0=22.2123972222 +lon_0=113.5364694444 +k=1 +x_0=20000 +y_0=20000 +ellps=intl +units=m +no_defs'
m = Map(256,256,proj4)
lyr = Layer('Name',proj4)