熊猫创建列并添加值

我有一个熊猫Dataframe pmap：

    name            quality_of_life_index
0   Afghanistan     NaN
1   Aland Islands   NaN
2   Albania         98.710473
3   Alderney        NaN
4   Algeria         98.686111

并get_country(country)返回短国家名称和大洲的函数：

get_country("Albania")

>> ('AL', 'EU')

我想在pmap中添加两列，并用以下值填充它们：

    name            quality_of_life_index  country    continent
0   Afghanistan     NaN                    Unknown    Unknown
1   Aland Islands   NaN                    Unknown    Unknown
2   Albania         98.710473              AL         EU
3   Alderney        NaN                    Unknown    Unknown
4   Algeria         98.686111              DZ         AF

我试过了

 for i in range(0, len(pmap)):
     names = get_continent(pmap['name'][i])
     pmap['country', 'continent'] = names

但它返回一个错误

ValueError: Length of values (2) does not match length of index (233)