FishHook
Обратное тоже верно. Кому хватает библиотек переписанных на тройку, можно наботать и на ней

o7412369815963
меня одно напрягает - как сделан уникод в py3, в py2 с кодировками гибче

py.user.next
чего ?

wmnpyafn
Можешь рассказать подробнее про запуск библиотек от Python 2 на python 3.

o7412369815963
вообще негатив про кодировки можно почитать в блоге у Армина Роначера

That might not seem like a big deal at first, but APIs have the attitude of spreading further. For instance opening a file will set the name attribute to a “string” of that type:

>>> open(b'/tmp/test/Schei\xc3\x9f_Encoding').name
b'/tmp/test/Schei\xc3\x9f_Encoding'

As a result every user of the .name attribute will have to force it to the right type before interacting with it. The same thing also has been true on 2.x, however on 3.x this behavior is mostly undocumented.

Python 3 unfortunately made a choice of guessing a little bit too much with unicode in some places. When I asked the question at one conference before about what people believe the default encoding for text files on Python 3 was, most were replying UTF-8. This is correct on some operating systems. It's definitely true for OS X and it's true for most linux distributions I tried. However how does Python determine that encoding? The answer is by looking into the locale settings in the environment variables.

>>> letter = '\N{LATIN CAPITAL LETTER U WITH DIAERESIS}'.encode('latin1')
>>> decoded_letter = letter.decode('utf-8', 'surrogateescape')
>>> decoded_letter
'\udcdc'
>>> decoded_letter.encode('utf-8')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'utf-8' codec can't encode character '\udcdc' in position 0: surrogates not allowed

>>> decoded_letter.encode('utf-8', 'surrogateescape')
b'\xdc'
>>>

This primarily means that you have two options: change all your encode() errorhandling anywhere in your codebase from ‘strict’ (which is the default) to ‘surrogateescape’ or remove surrogates from your strings.

o7412369815963
пропала возможность дважды декодировать

b''.decode().decode()

o7412369815963
пропала возможность дважды декодировать b''.decode().decode()

There should be one-- and preferably only one --obvious way to do it.

py.user.next
его статья

>>> b'123' == u'123'
False
>>> b'123' + u'123'
Traceback (most recent call last):
File “<stdin>”, line 1, in <module>
TypeError: can't concat bytes to str

o7412369815963
Скорее эта

>>> '\xe2\x98\x83'.encode('utf-8')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 0: ordinal not in range(128)
>>>

o7412369815963
в py3 print “принимает” только строки

o7412369815963
в py2 результат будет “обратный”

>>> list(b'abc')
[97, 98, 99]
>>>

>>> list(b'abc')
['a', 'b', 'c']
>>> b'abc'[0][0][0]
'a'
>>>