from functools import lru_cache

class Weather:
    "Example with a mutable station identifier"

    def __init__(self, station_id):
        self.station_id = station_id

    def change_station(self, station_id):
        self.station_id = station_id

    def __eq__(self, other):
        return self.station_id == other.station_id

    def __hash__(self):
        return hash(self.station_id)

    @lru_cache(maxsize=20)
    def historic_rainfall(self, date, units='cm'):
        print('...recomputing')
        return f'Rainfall on a given date (for: {self.station_id}, {date}, {units})'


print("Weather(1)")
w1 = Weather(1)
print(w1.historic_rainfall('day1'))
w1.change_station(2)

print("Weather(1) again")
print(Weather(1).historic_rainfall('day1'))

output = '''\
$ python3 t3.py
Weather(1)
...recomputing
Rainfall on a given date (for: 1, day1, cm)
Weather(1) again
...recomputing
Rainfall on a given date (for: 1, day1, cm)
'''