Version 25 (modified by mtredinnick, 8 years ago) (diff)

The 5-step porting guide now comes with 20% extra free stuff (yeah, I'm dumb... I forgot a step)


The unicode branch

This branch aims to make Django's internals fully Unicode-aware.

How to get the branch

svn co

See our branch policy for full information on how to use a branch.


The main goals of this branch are:

  • Make it easier for developers to work with non-ASCII character data when working with Django.
  • Be more consistent in our string handling behaviour inside Django (see StringEncoding for details on this).

Upon completion, you will be able to pass around unicode strings anywhere inside Django (or between Django and developer applications).

Note that we are not trying to switch to forcing everybody to only use unicode strings. You will also be able to pass around bytestrings and Django will assume they are UTF-8 encoded (we have to make an assumption because there is no way to tell what the encoding is otherwise). This feature means that a large chunk of existing code that uses Django will continue to work unchanged.


The branch was created on April 7, 2007.

Reported bugs from trunk that have been fixed and will be closed once the branch is merged back into trunk can be viewed here.

Todo Items

The various pieces will be converted in roughly the following order:

  1. Template rendering (Done in [4971])
  2. Database I/O (Done in [4971] for postgresql, postgresql_psycopg2, mysql, mysql_old and sqlite backends)
    • Needs testing for servers/tables that are not in UTF-8 or ASCII encoding. The theory is that the client connection for each backend should be automatically converting everything to UTF-8 or Unicode objects (depends on backend), but this needs verifying. (Ivan Sagalaev and Malcolm have tested this feature a fair bit with various database servers, but more stress tests would be nice.)
  3. Model class support (Done in [5057])
  4. Form input encoding (Done in [5192])
  5. Other output methods:
    • syndication (Done in [5251])
    • serialization (Done in [5248])
    • Google sitemaps (Done in [5277])
  6. Audit other contrib modules (not all will require changes) (all Done as of [5274]).
  7. Verifying and fixing all bugs mentioned in Trac.
    • This includes the 9 tickets that were merged in #2489 (all Done, except for upgrading slug generation to be a little more useful with some foreign character sets.)

We also need to look at the i18n support functions (in django.utils.translation):

  • Decide on usage of gettext() versus ugettext() in a number of places (Done. Recommended to use ugettext() and friends everywhere. In [5230] this change has been made throughout the framework).
  • Look at fixing ugettext_lazy() so that it acts as a better string and unicode proxy. (Done: lots of fixes over a few commits to get this right, but it seems to be working well now, as least as s a unicode proxy, which is what is important.)

Finally, some documentation needs to be written describing good practices for creating unicode-aware Django apps.

Porting Applications (The Quick Checklist)

One of the design goals of the Unicode branch is that very little significant changes to existing third-party code should be required. However, there are some things that developers should be aware of when writing applications designed to handle international input.

A detailed list of things you might wish to think about when writing your code is in the unicode.txt file in the documentation directory. For the programmer on a deadline, here is the cheatsheet version (if you only use ASCII strings, none of these changes are necessary):

(Note (25 May 2007): Early adopters will have seen five steps in this list. The all-important step number 3 was initially omitted.)

  1. Change the __str__ methods on your models to be __unicode__ methods. Just change the name. Usually, nothing else will be needed.
  1. Look for any str() calls in your code that operate on model fields. These should almost always be changed to smart_unicode() calls (which is imported from django.utils.encoding). In some cases, you may need to use force_unicode() (in the same module), but starting with a global change to smart_unicode() and then checking for problems is the "quick fix" way. (Details of the differences between the two functions are in unicode.txt.)
  1. Change your string literals that include Python format characters to be unicode strings. For example, change this:
    formal_name = '%s %s %s' % (title, firstname, surname)     # old version
    to this:
    formal_name = u'%s %s %s' % (title, firstname, surname)    # new version
    This is useful for two reasons. Firstly, if the parameters contain non-ASCII characters, you won't have an exception raised. Secondly, if any of the parameters are objects, Python will automaticay call their __unicode__ method and convert them to the right type. The "before" code would have resulted in the __str__ method being called instead. Of course, this step is only a good idea if you are interpolating unicode strings. If your parameters are bytestrings, they will not automatically be decoded to unicode strings before being interpolated (Python cannot read your mind). Use smart_unicode() for that purpose.
    • Warning for Python 2.3: There is a bug in the way Python 2.3 does string interpolation for unicode strings that you should be aware of if your code has to work with that verison of Python. In the second line of code, above, if any of the parameters are non-basestring objects, Python will call the __str__ method on the object, not the __unicode__ method! So, for Python 2.3-compatible code, you would need to write something like
      some_string = u'This is your object: %s' % unicode(some_object)
      Note the explicit call to unicode() here to force the object to be the right type.
  1. Use the unicode versions of the django.utils.translation.* functions. Replace gettext and ngettext with ugettext and ungettext respectively. There are also ugettext_lazy and ungettext_lazy functions if you use the lazy versions.
  1. Make sure your database can store all the data you will send to it. Usually, this means ensuring it is using UTF-8 (or similar) encoding internally.
  1. Use the FILE_CHARSET setting if your on-disk template files and initial SQL files are not UTF-8 encoded.

That is all. Enjoy!

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