IDNA vs Punycode

idna-punycode.pycon

Python 3.5.1 (default, Dec  7 2015, 12:58:09) 
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In [1]: 'ąbc.pl'.encode('punycode')
Out[1]: b'bc.pl-2wa'

In [2]: 'abc.pl'.encode('punycode')
Out[2]: b'abc.pl-'

In [3]: 'ąbc.pl'.encode('punycode')
Out[3]: b'bc.pl-2wa'

In [4]: 'ąbc.pl'.encode('idna')
Out[4]: b'xn--bc-ola.pl'

In [5]: 'abc.pl'.encode('punycode')
Out[5]: b'abc.pl-'

In [6]: 'abc.pl'.encode('idna')
Out[6]: b'abc.pl'

In [7]: 'ąbc'.encode('punycode')
Out[7]: b'bc-ola'

In [8]: 'ąbc'.encode('idna')
Out[8]: b'xn--bc-ola'