data_processing.py

import csv, os

__location__ = os.path.realpath(
    os.path.join(os.getcwd(), os.path.dirname(__file__)))

cities = []
with open(os.path.join(__location__, 'Cities.csv')) as f:
    rows = csv.DictReader(f)
    for r in rows:
        cities.append(dict(r))

countries = []
with open(os.path.join(__location__, 'Countries.csv')) as f:
    rows = csv.DictReader(f)
    for r in rows:
        countries.append(dict(r))

# Print the average temperature for all the cities in Italy
temps = []
my_country = 'Italy'
for city in cities:
    if city['country'] == my_country:
        temps.append(float(city['temperature']))
print(sum(temps)/len(temps))  

print()
# Print all cities that are not in the EU and whose average temperatures are below 5.0
# Requires joining cities and countries
import copy
cities_ext = []
for city in cities:
    for country in countries:
        if city['country'] == country['country']:
            dict1 = copy.deepcopy(city)
            dict2 = copy.deepcopy(country)
            dict1.update(dict2)
            cities_ext.append(dict1)
for city in cities_ext:
    if city['EU'] == 'no' and float(city['temperature']) < 5.0:
        print(city)