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

def has_cell_methods(cube):
    cm = cube.cell_methods
    return len(cm) > 0

cm_constraint = iris.Constraint(cube_func=has_cell_methods)

a1b_fname = iris.sample_data_path('A1B_north_america.nc')
colpex_fname = iris.sample_data_path('colpex.pp')
ostia_fname = iris.sample_data_path('ostia_monthly.nc')

cubelist = iris.load([a1b_fname, colpex_fname, ostia_fname])
for cube in cubelist:
    print('{}\n\tCell Methods = {}\n'.format(cube.summary(True), cube.cell_methods))

print cubelist.extract(cm_constraint)

interval_6_hr = iris.coords.CellMethod('mean', coords='time', intervals='6 hour')
constraint_6_hr = iris.Constraint(cube_func=lambda cube: interval_6_hr in cube.cell_methods)

print cubelist.extract(constraint_6_hr)