Django无法处理非ASCII符号。

Question

我们遇到了一个奇怪的问题。如果在 Django 中使用非 ASCII 符号，它会在列表中正常显示，但是如果我们尝试进入该项，则会出现以下错误：

sys.setdefaultencoding("utf-8")可以帮助解决问题，但有一种观点认为这是错误的做法（为什么我们不应该在Python脚本中使用sys.setdefaultencoding("utf-8")?）。那么正确的解决方法是什么？为什么列表显示正常？欢迎提出任何想法！

完整的回溯信息：

Environment:


Request Method: GET
Request URL: http://127.0.0.1:8000/enter/event/23/change/

Django Version: 1.9.4
Python Version: 2.7.10
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'debug_toolbar',
 'enter']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'debug_toolbar.middleware.DebugToolbarMiddleware']


Template error:
In template /Library/Python/2.7/site-packages/django/contrib/admin/templates/admin/change_form.html, error at line 21
   ascii   11 : {% block coltype %}colM{% endblock %}
   12 : 
   13 : {% block bodyclass %}{{ block.super }} app-{{ opts.app_label }} model-{{ opts.model_name }} change-form{% endblock %}
   14 : 
   15 : {% if not is_popup %}
   16 : {% block breadcrumbs %}
   17 : <div class="breadcrumbs">
   18 : <a href="{% url 'admin:index' %}">{% trans 'Home' %}</a>
   19 : &rsaquo; <a href="{% url 'admin:app_list' app_label=opts.app_label %}">{{ opts.app_config.verbose_name }}</a>
   20 : &rsaquo; {% if has_change_permission %}<a href="{% url opts|admin_urlname:'changelist' %}">{{ opts.verbose_name_plural|capfirst }}</a>{% else %}{{ opts.verbose_name_plural|capfirst }}{% endif %}
   21 : &rsaquo; {% if add %}{% trans 'Add' %} {{ opts.verbose_name }}{% else %} {{ original|truncatewords:"18" }} {% endif %}
   22 : </div>
   23 : {% endblock %}
   24 : {% endif %}
   25 : 
   26 : {% block content %}<div id="content-main">
   27 : {% block object-tools %}
   28 : {% if change %}{% if not is_popup %}
   29 :   <ul class="object-tools">
   30 :     {% block object-tools-items %}
   31 :     <li>


Traceback:

File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response
  174.                     response = self.process_exception_by_middleware(e, request)

File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response
  172.                     response = response.render()

File "/Library/Python/2.7/site-packages/django/template/response.py" in render
  160.             self.content = self.rendered_content

File "/Library/Python/2.7/site-packages/django/template/response.py" in rendered_content
  137.         content = template.render(context, self._request)

File "/Library/Python/2.7/site-packages/django/template/backends/django.py" in render
  95.             return self.template.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  206.                     return self._render(context)

File "/Library/Python/2.7/site-packages/django/test/utils.py" in instrumented_test_render
  92.     return self.nodelist.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/Library/Python/2.7/site-packages/django/template/loader_tags.py" in render
  173.         return compiled_parent._render(context)

File "/Library/Python/2.7/site-packages/django/test/utils.py" in instrumented_test_render
  92.     return self.nodelist.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/Library/Python/2.7/site-packages/django/template/loader_tags.py" in render
  173.         return compiled_parent._render(context)

File "/Library/Python/2.7/site-packages/django/test/utils.py" in instrumented_test_render
  92.     return self.nodelist.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/Library/Python/2.7/site-packages/django/template/defaulttags.py" in render
  326.                 return nodelist.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/Library/Python/2.7/site-packages/django/template/loader_tags.py" in render
  69.                 result = block.nodelist.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/Library/Python/2.7/site-packages/django/template/defaulttags.py" in render
  326.                 return nodelist.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in render
  1043.             output = self.filter_expression.resolve(context)

File "/Library/Python/2.7/site-packages/django/template/base.py" in resolve
  736.                 new_obj = func(obj, *arg_vals)

File "/Library/Python/2.7/site-packages/django/template/defaultfilters.py" in _dec
  47.             args[0] = force_text(args[0])

File "/Library/Python/2.7/site-packages/django/utils/encoding.py" in force_text
  80.                 s = six.text_type(bytes(s), encoding, errors)

Exception Type: UnicodeEncodeError at /enter/event/23/change/
Exception Value: 'ascii' codec can't encode character u'\xe9' in position 29: ordinal not in range(128)

- Arkady

---

请发布完整的回溯（作为文本）。还要检查您的 settings.DEFAULT_CHARSET 和数据库编码（表和客户端）。 - bruno desthuilliers

你的 settings.DEFAULT_CHARSET 是什么？你的模型字段标签或帮助文本中是否有重音字符？这个问题只出现在某些记录上还是所有记录上都有？如果尝试从管理员创建新事件，你是否遇到了这个问题？ - bruno desthuilliers

@scharette Django使用“Unicode三明治”模式，因此模板期望Unicode字符串并负责对它们进行编码。 - bruno desthuilliers

@Arkady 无法在未检查您的代码的情况下确定原因 - 这里有许多因素，包括是否使用 from __future__ import unicode_literals 或者是否正确使用了 u"" 的 Unicode 前缀，如果您的源代码中有 # -*- coding: <encoding_name> 头文件，以及您的 __unicode__ 方法是如何实现的等等... 关于 settings.DEFAULT_CHARSET，如果未设置，则默认为 utf-8，由于您的错误消息明确提到了 ascii 编解码器，因此它确实不是罪魁祸首。 - bruno desthuilliers

作为一般规则：如果你想要安全，你需要始终只在代码中使用unicode，尤其是对于文字字符串。Django本身会将一切在系统入口点（如HTTP查询、数据库查询等）转换为unicode。 - bruno desthuilliers

Answer 1

在我的情况下，用 __unicode__ 方法替换 __str__ 方法有所帮助，但是正如 @bruno-desthuilliers 所说，这里有许多因素需要考虑。

# def __str__(self):
#     return str(self.id) +': ' + self.title

def __unicode__(self):
    return u'%s: %s' % (self.id, self.title)

- Arkady

---

绝对不要从__unicode __()返回一个str！它必须是一个Unicode字符串。这里的正确实现应该是return u"{}: {}".format(self.id, self.title)。 - bruno desthuilliers