data_country1 = {'Country': [np.NaN, 'India', 'Brazil'],'Capital': [np.NaN, 'New Delhi', 'Brasília'],'Population': [np.NaN, 1303171035, 207847528]}
df_country1 = pd.DataFrame(data_country1, columns=['Country', 'Capital', 'Population'])
#df_country1 = df_country1.fillna(value=0)
print(df_country1)

data_country2= {'Country': ['Belgium', 'India', 'Brazil'],'Capital': ['Brussels', 'New Delhi', 'Brasília'],'Population': [102283932, 1303171035, 207847528]}
df_country2 = pd.DataFrame(data_country2, columns=['Country', 'Capital', 'Population'])
print(df_country2)

Country    Capital    Population
0     NaN        NaN           NaN
1   India  New Delhi  1.303171e+09
2  Brazil   Brasília  2.078475e+08

   Country    Capital  Population
0  Belgium   Brussels   102283932
1    India  New Delhi  1303171035
2   Brazil   Brasília   207847528