解决django ImportError: Settings cannot be imported错误

转：http://www.iyouf.info/fixed-django-settings-error.html
今天在练习django的模板引擎的时候出了这么一个错误

ImportError: Settings cannot be imported, because environment variable DJANGO_SETTINGS_MODULE is undefined.

root@ubuntu:~# python
Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from django.template import Template
>>> t = Template("my name is {{name}}")
Traceback (most recent call last):
File "", line 1, in
File "/usr/local/lib/python2.6/dist-packages/django/template/__init__.py", line 156, in __init__
if settings.TEMPLATE_DEBUG and origin is None:
File "/usr/local/lib/python2.6/dist-packages/django/utils/functional.py", line 276, in __getattr__
self._setup()
File "/usr/local/lib/python2.6/dist-packages/django/conf/__init__.py", line 38, in _setup
raise ImportError("Settings cannot be imported, because environment variable %s is undefined." % ENVIRONMENT_VARIABLE)
ImportError: Settings cannot be imported, because environment variable DJANGO_SETTINGS_MODULE is undefined.
这是因为我在命令行下使用python命令进入交互模式的，Template(str)在构照模板的时候依赖django.conf.settings.这个变量，但是在当前的环境中没有这个变量,这时，它就会抛出异常了


办法就是 要想使用django的模板你必须导入settings
>>> from django.conf import settings
>>> settings.configure()
你在运行t = Template("my name is {{name}}") 就不会出错了

还有一种方法就是使用python manager.py shell运行

root@ubuntu:/home/python/cms# python manage.py shell
Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.template import Template,Context
>>> t=Template('my name is {{name}}')
>>> c=Context({'name':'dengmin'})
>>> t.render(c)
u'my name is dengmin'
>>>
这是因为python manager.py shell的时候djano会去查找settings.py，这个文件包含了这个Django实例的所有配置选项

打开这个文件我们可以看到这样的配置

# List of callables that know how to import templates from various sources.
TEMPLATE_LOADERS = (
    'django.template.loaders.filesystem.Loader',
    'django.template.loaders.app_directories.Loader',
#     'django.template.loaders.eggs.Loader',
)
这个是django提供的模板加载器

在目录/usr/local/lib/python2.6/dist-packages/django/template/loaders下找到这两个文件

filesystem.py app_directories.py，这两个文件中都导入from django.conf import settings

最后，在使用django的模板时，应该使用python manager.py shell来进入交互模式，这样可以避免很多不必要的麻烦