The keys method of dictionary class

# Example Python program that retrieves
# all the keys of a dictionary as a dict_keys
airports = {"ATL":"Hartsfield Atlanta International",
             "BWI":"Washington DC - Baltimore Washington International",
             "DFW":"Dallas/Fort Worth International" ,
             "JFK":"New York - John F. Kennedy",
             "LAX":"Los Angeles",
             "ORD":"Chicago - O'Hare International",
             "SFO":"San Francisco",
           };

airport_codes = airports.keys();

print("Dictionary view:");

# Iterate the view and print the airport codes
for code in airport_codes:
    print(code);

# Add more airport codes
airports["EWR"] = "Newark";
airports["DEN"] = "Denver";

# Print the view after changes to the original dictionary
print("New dictionary view:");
for code in airport_codes:
    print(code);