Creating utility functions to generate maps

Now we will create the first function that will compose our application.

1. Still in the mapnik_experiments folder, create a new file: map_functions.py.

2. Insert the code as follows into that file:

   # coding=utf-8
   
   import mapnik
   
   
   def create_map(style_file, output_image, size=(800, 600)):
       """Creates a map from a XML file and writes it to an image.
   
       :param style_file: Mapnik XML file.
       :param output_image: Name of the output image file.
       :param size: Size of the map in pixels.
       """
       map = mapnik.Map(*size)
       mapnik.load_map(map, style_file)
       map.zoom_all()
       mapnik.render_to_file(map, output_image)
   
   
   if __name__ == '__main__':
       create_map('map_style.xml', '../output/world3.png',
                  size=(400, 400))

What we did here is pack the map generation code into a function that we can reuse in the future. It takes two required arguments: the XML style file and the name of the image file that Mapnik will write the results to...