python - Problem storing Unicode character to MySQL with Django

Question

I have the string

 u"Played Mirror's Edge\u2122"

Which should be shown as

 Played Mirror's Edge™

But that is another issue. My problem at hand is that I'm putting it in a model and then trying to save it to a database. AKA:

a = models.Achievement(name=u"Played Mirror's Edge\u2122")
a.save()

And I'm getting :

'ascii' codec can't encode character u'\u2122' in position 13: ordinal not in range(128)

full stack trace (as requested) :

Traceback:
File "/var/home/ptarjan/django/mysite/django/core/handlers/base.py" in get_response
  86.                 response = callback(request, *callback_args, **callback_kwargs)
File "/var/home/ptarjan/django/mysite/yourock/views/alias.py" in import_all
  161.     types.import_all(type, alias)
File "/var/home/ptarjan/django/mysite/yourock/types/types.py" in import_all
  52.     return modules[type].import_all(siteAlias, alias)
File "/var/home/ptarjan/django/mysite/yourock/types/xbox.py" in import_all
  117.             achiever = self.add_achievement(dict, siteAlias, alias)
File "/var/home/ptarjan/django/mysite/yourock/types/base_profile.py" in add_achievement
  130.                 owner       = siteAlias,
File "/var/home/ptarjan/django/mysite/django/db/models/query.py" in get
  304.         num = len(clone)
File "/var/home/ptarjan/django/mysite/django/db/models/query.py" in __len__
  160.                 self._result_cache = list(self.iterator())
File "/var/home/ptarjan/django/mysite/django/db/models/query.py" in iterator
  275.         for row in self.query.results_iter():
File "/var/home/ptarjan/django/mysite/django/db/models/sql/query.py" in results_iter
  206.         for rows in self.execute_sql(MULTI):
File "/var/home/ptarjan/django/mysite/django/db/models/sql/query.py" in execute_sql
  1734.         cursor.execute(sql, params)
File "/var/home/ptarjan/django/mysite/django/db/backends/util.py" in execute
  19.             return self.cursor.execute(sql, params)
File "/var/home/ptarjan/django/mysite/django/db/backends/mysql/base.py" in execute
  83.             return self.cursor.execute(query, args)
File "/usr/lib/pymodules/python2.5/MySQLdb/cursors.py" in execute
  151.             query = query % db.literal(args)
File "/usr/lib/pymodules/python2.5/MySQLdb/connections.py" in literal
  247.         return self.escape(o, self.encoders)
File "/usr/lib/pymodules/python2.5/MySQLdb/connections.py" in string_literal
  180.                 return db.string_literal(obj)

Exception Type: UnicodeEncodeError at /import/xbox:bob
Exception Value: 'ascii' codec can't encode character u'\u2122' in position 13: ordinal not in range(128)

And the pertinant part of the model :

class Achievement(MyBaseModel):
    name = models.CharField(max_length=100, help_text="A human readable achievement name")

I'm using a MySQL backend with this in my settings.py

DEFAULT_CHARSET = 'utf-8'

So basically, how the heck should I deal with all this unicode stuff? I was hoping it would all "just work" if I stayed away from funny character sets and stuck to UTF8. Alas, it seems to not be just that easy.

Answer 1

Thank you to everyone who was posting here. It really helps my unicode knowledge (and hoepfully other people learned something).

We seemed to be all barking up the wrong tree since I tried to simplify my problem and didn't give ALL information. It seems that I wasn't using "REAL" unicode strings, but rather BeautifulSoup.NavigableString which repr themselves as unicode strings. So all the printouts looked like unicode, but they weren't.

Somewhere deep in the MySQLDB library they couldn't deal with these strings.

This worked :

>>> Achievement.objects.get(name = u"Mirror's Edge\u2122")
<Achievement: Mirror's Edge™>

On the other hand :

>>> b = BeautifulSoup(u"<span>Mirror's Edge\u2122</span>").span.string
>>> Achievement.objects.get(name = b)
... Exceptoins ...
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2122' in position 13: ordinal not in range(128)

But this works :

>>> Achievement.objects.get(name = unicode(b))
<Achievement: Mirror's Edge™>

So, thanks again for all the unicode help, I'm sure it will come in handy. But for now ...

WARNING : BeautifulSoup doesn't return REAL unicode strings and should be coerced with unicode() before doing anything meaningful with them.

Answer 2

A few remarks:

• Python 2.x has two string types

  • "str", which is basically a byte array (so you can store anything you like in it)
  • "unicode" , which is UCS2/UCS4 encoded unicode internally

• Instances of these types are considered "decoded" data. The internal representation is the reference, so you "decode" external data into it, and "encode" into some external format.

• A good strategy is to decode as early as possible when data enters the system, and encode as late as possible. Try to use unicode for the strings in your system as much as possible. (I disagree with Nikolai in this regard).

• This encoding aspect applies to Nicolai's answer. He takes the original unicode string, and encodes it into utf-8. But this doesn't solve the problem (at least not generally), because the resulting byte buffer can still contain bytes outside the range(127) (I haven't checked for \u2122), which means you will hit the same exception again.

• Still Nicolai's analysis holds that you are passing a unicode string, but somewhere down in the system this is regarded a str instance. It suffices if somewhere the str() function is applied to your unicode argument.

• In that case Python uses the so called default encoding which is ascii if you don't change it. There is a function sys.setdefaultencoding which you can use to switch to e.g. utf-8, but the function is only available in a limited context, so you cannot easily use it in application code.

• My feeling is the problem is somewhere deeper in the layers you are calling. Unfortunately, I cannot comment on Django or MySQL/SQLalchemy, but I wonder if you could specify a unicode type when declaring the 'name' attribute in your model. It would be good DB practice to handle type information on the field level. Maybe there is an alternative to CharField?!

• And yes, you can safely embed a single quote (') in a double quoted (") string, and vice versa.