[Python-Dev] Inconsistency in 2.4.3 for __repr__() returning unicode

[M.-A. Lemburg]

Hye-Shik Chang wrote:
> We got an inconsistency for __repr__() returning unicode as
> reported in http://python.org/sf/1459029 :
> 
> class s1:
>     def __repr__(self):
>         return '\\n'
> 
> class s2:
>     def __repr__(self):
>         return u'\\n'
> 
> print repr(s1()), repr(s2())
> 
> Until 2.4.2: \n \n
> 2.4.3: \n \\n
> 
> \\n looks bit weird but it's correct.  As once discussed[1] in
> python-dev before, if __repr__ returns unicode object,
> PyObject_Repr encodes it via unicode-escape codec.  So,
> non-latin character also could be in repr neutrally.

I don't think that using unicode-escape is the right choice
for converting a string returned by __repr__ to a string -
why would you want to escape a Unicode string that was
specifically prepared to provide the representation of
an object ?

> But our unicode-escape had a bug since when it is introduced.
> The bug was that it doesn't escape backslashes.  Therefore,
> backslashes wasn't escaped in repr while it sholud be escaped
> because we used the unicode-escape codec.
> 
> So, fixing the bug made a behavior inconsistency.
> How do we resolve the problem?

Change PyObject_Repr() to use the default encoding (again)
which is also consistent with how PyObject_Str() works.

To make repr() conversion more robust, we could have
PyObject_Repr() apply the conversion using the 'replace'
error strategy - after all, repr() is usually only
used for debugging, where it's more important that
you do get an output rather than an exception.

> Hye-Shik
> 
> 
> [1] http://mail.python.org/pipermail/python-dev/2000-July/005353.html

-- 
Marc-Andre Lemburg
eGenix.com

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