ISO 3166-1 defines two-letter, three-letter, and three-digit country codes. python-iso3166 is a self-contained module that converts between these codes and the corresponding country name.

$ pip install iso3166

>>> from iso3166 import countries
>>>
>>> countries.get('us')
Country(name='United States', alpha2='US', alpha3='USA', numeric='840')
>>> countries.get('ala')
Country(name='Åland Islands', alpha2='AX', alpha3='ALA', numeric='248')
>>> countries.get(8)
Country(name='Albania', alpha2='AL', alpha3='ALB', numeric='008')

>>> from iso3166 import countries

>>> for c in countries:
       print(c)
>>> Country(name='Afghanistan', alpha2='AF', alpha3='AFG', numeric='004')
Country(name='Åland Islands', alpha2='AX', alpha3='ALA', numeric='248')
Country(name='Albania', alpha2='AL', alpha3='ALB', numeric='008')
Country(name='Algeria', alpha2='DZ', alpha3='DZA', numeric='012')

>>> import iso3166

>>> iso3166.countries_by_name
>>> {'AFGHANISTAN': Country(name='Afghanistan', alpha2='AF', alpha3='AFG', numeric='004'),
'ALBANIA': Country(name='Albania', alpha2='AL', alpha3='ALB', numeric='008'),
'ALGERIA': Country(name='Algeria', alpha2='DZ', alpha3='DZA', numeric='012'),
...

>>> iso3166.countries_by_numeric
>>> {'004': Country(name='Afghanistan', alpha2='AF', alpha3='AFG', numeric='004'),
'008': Country(name='Albania', alpha2='AL', alpha3='ALB', numeric='008'),
'010': Country(name='Antarctica', alpha2='AQ', alpha3='ATA', numeric='010'),
...

>>> iso3166.countries_by_alpha2
>>> {'AD': Country(name='Andorra', alpha2='AD', alpha3='AND', numeric='020'),
'AE': Country(name='United Arab Emirates', alpha2='AE', alpha3='ARE', numeric='784'),
'AF': Country(name='Afghanistan', alpha2='AF', alpha3='AFG', numeric='004'),
...

>>> iso3166.countries_by_alpha3
>>> {'ABW': Country(name='Aruba', alpha2='AW', alpha3='ABW', numeric='533'),
'AFG': Country(name='Afghanistan', alpha2='AF', alpha3='AFG', numeric='004'),
'AGO': Country(name='Angola', alpha2='AO', alpha3='AGO', numeric='024'),
...