d = {3: "Earth", 1: "Mercury", 4: "Mars", 2: "Venus"}
for k in sorted(d):
    print("%i: %s" % (k, d[k]))

d = {"London": "United Kingdom", "Berlin": "Germany", "Rome": "Italy", "Paris": "France"}
for k in sorted(d):
    print("%s: %s" % (k, d[k]))