#3924: Caught an exception while rendering: 'ascii' codec can't decode byte 0xc3
in position 8: ordinal not in range(128)
--------------------------------------------+-------------------------------
Reporter: ruben.pe...@gmail.com | Owner: hugo
Status: closed | Milestone:
Component: django.contrib.admin | Version: 1.0
Resolution: fixed | Keywords:
Stage: Accepted | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by kmtracey):
Yes, Python's behavior here can cause some confusion. Note `"%s" % x` may
evaluate to either Unicode or a bytestring depending on the type of x:
{{{
#!python
>>> u = u"Unicode!"
>>> b = 'Bytestring'
>>> "%s" % u
u'Unicode!'
>>> "%s" % b
'Bytestring'
}}}
This is why you often won't see a problem with your Visitor `__unicode__`
as originally coded: usually the `lastName` and `firstName` attributes
will be Unicode values, so `"%s %s" % (self.lastName,self.firstName)` will
evaluate to a Unicode value and you won't see a problem.
For more complicated situations, say a class that supports both `__str__`
and `__unicode__`, whether or not you specify `u''` on the interpolation
will control what type of result you get:
{{{
#!python
>>> class Thing(object):
... def __init__(self, x):
... self.x = x
... def __str__(self):
... return self.x.encode('utf-8')
... def __unicode__(self):
... return self.x
...
>>> t = Thing(u'\u0101')
>>> "%s" % t
'\xc4\x81'
>>> u"%s" % t
u'\u0101'
}}}
This is where your Visit `__unicode__` method as originally coded has a
problem. `self.visitor` has both `__str__` and `__unicode__` methods, so
unless you force the `__unicode__` one to be called by using `u''` for the
interpolation, the result will be a bytestring, and if that contains non-
ascii chars then the automatic coercion to unicode using the ascii codec
will generate an exception.
{{{
#!python
>>> unicode("%s" % t)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc4 in position 0:
ordinal not in range(128)
>>>
}}}
So yes, sometimes it seems like you don't necessarily absolutely need the
`u''` for the `__unicode__` return value. But figuring out when exactly
you need it and when you don't can be complicated so it's a good idea to
use it as a matter of routine.
--
Ticket URL: <http://code.djangoproject.com/ticket/3924#comment:30>
Django <http://code.djangoproject.com/>
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