We can also include a column name which is not contained in the dictionary. In this case, all the values of this column will be set to NaN:
city_frame = pd.DataFrame(cities,
columns=["country",
"area",
"population"],
index=cities["name"])
print(city_frame)
country area population
name
London England NaN 8615246
Berlin Germany NaN 3562166
Madrid Spain NaN 3165235
Rome Italy NaN 2874038
Paris France NaN 2273305
Vienna Austria NaN 1805681
Bucharest Romania NaN 1803425
Hamburg Germany NaN 1760433