from sets import Set
countriesStats = {
    'Nigeria' : {'area': 923768, 'population': 182202000, 'languages': ['English']},
    'South Africa' : {'area': 1219912, 'population': 54490000, 'languages': ['Zulu', 'Xhosa', 'Afrikaans', 'English']},
    'Ethiopia' : { 'area': 1127127, 'population': 99391000, 'languages': ['Amharic']}
}
languagesSpoken = Set()

# Part 1
countriesStats["Kenya"] = {'area': 582646, 'population': 47615739, 'languages': ['Kishwahili', 'English']}

# Part 2
for country in countriesStats:
    countriesStats[country]["population density"] = countriesStats[country]["population"] / float(countriesStats[country]["area"])
    # optional to solve also Part 3
    for language in countriesStats[country]["languages"]:
        languagesSpoken.add(language)

# Part 3
for country in countriesStats:
    for language in countriesStats[country]["languages"]:
        languagesSpoken.add(language)