import cartopy.io.shapereader as shpreader
import iris
import iris.analysis.geometry as iag

print('Iris version: {}'.format(iris.__version__))

a1b_cube = iris.load_cube(iris.sample_data_path('A1B.2098.pp'))
lats = a1b_cube.coord('latitude')
lons = a1b_cube.coord('longitude')
if not lats.has_bounds():
    lats.guess_bounds()
if not lons.has_bounds():
    lons.guess_bounds()

filename = shpreader.natural_earth(resolution='110m',
                                   category='cultural',
                                   name='admin_0_countries')
borders = shpreader.Reader(filename)
uk_geom, = [g for g in borders.records() if g.attributes['name_long']=='United Kingdom']

print uk_geom.attributes.keys()

weights = iag.geometry_area_weights(a1b_cube, uk_geom.geometry)
cube_collapsed = a1b_cube.collapsed(['latitude', 'longitude'],
                                    iris.analysis.MEAN,
                                    weights=weights)
print('Average UK air temp in 2098: {:.3f}K'.format(cube_collapsed.data[0]))