Why does unicode-escape decode escape symbols that are already escaped?

[Albert-Jan Roskam]

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On Sun, May 10, 2015 5:53 PM CEST Somelauw . wrote:

>In Python 3, decoding "€" with unicode-escape returns 'â\x82¬' which in my
>opinion doesn't make sense.
>The € already is decoded; if it were encoded it would look like this:
>'\u20ac'.
>So why is it doing this?
>
>In Python 2 the behaviour is similar, but slightly different.
>
>$ python3 -S
>Python 3.3.3 (default, Nov 27 2013, 17:12:35)
>[GCC 4.8.2] on linux
>>> import codecs
>>> codecs.decode('€', 'unicode-escape')
>'â\x82¬'
>>> codecs.encode('€', 'unicode-escape')
>b'\\u20ac'
>>>
>
>$ python2 -S
>Python 2.7.5+ (default, Sep 17 2013, 15:31:50)
>[GCC 4.8.1] on linux2
>>> import codecs
>>> codecs.decode('€', 'unicode-escape')
>u'\xe2\x82\xac'
>>> codecs.encode('€', 'unicode-escape')
>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)
>>>

Hi,

I only have Python 2 on my phone, but I am suprised that you (and are able to) decode unicode strings. What result do you get when you do the following in Python 3:

Python 2.7.2 (default, Oct 25 2014, 20:52:15)
[GCC 4.9 20140827 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import codecs
>>> codecs.decode(b'€', 'unicode-escape')
u'\xe2\x82\xac'
>>> codecs.encode(u'€', 'unicode-escape')
'\\xe2\\x82\\xac'
>>>