app/django/conf/__init__.py

   1 """
   2 Settings and configuration for Django.
   3
   4 Values will be read from the module specified by the DJANGO_SETTINGS_MODULE environment
   5 variable, and then from django.conf.global_settings; see the global settings file for
   6 a list of all possible variables.
   7 """
   8
   9 import os
  10 import time     # Needed for Windows
  11 from django.conf import global_settings
  12
  13 ENVIRONMENT_VARIABLE = "DJANGO_SETTINGS_MODULE"
  14
  15 class LazySettings(object):
  16     """
  17     A lazy proxy for either global Django settings or a custom settings object.
  18     The user can manually configure settings prior to using them. Otherwise,
  19     Django uses the settings module pointed to by DJANGO_SETTINGS_MODULE.
  20     """
  21     def __init__(self):
  22         # _target must be either None or something that supports attribute
  23         # access (getattr, hasattr, etc).
  24         self._target = None
  25
  26     def __getattr__(self, name):
  27         if self._target is None:
  28             self._import_settings()
  29         if name == '__members__':
  30             # Used to implement dir(obj), for example.
  31             return self._target.get_all_members()
  32         return getattr(self._target, name)
  33
  34     def __setattr__(self, name, value):
  35         if name == '_target':
  36             # Assign directly to self.__dict__, because otherwise we'd call
  37             # __setattr__(), which would be an infinite loop.
  38             self.__dict__['_target'] = value
  39         else:
  40             if self._target is None:
  41                 self._import_settings()
  42             setattr(self._target, name, value)
  43
  44     def _import_settings(self):
  45         """
  46         Load the settings module pointed to by the environment variable. This
  47         is used the first time we need any settings at all, if the user has not
  48         previously configured the settings manually.
  49         """
  50         try:
  51             settings_module = os.environ[ENVIRONMENT_VARIABLE]
  52             if not settings_module: # If it's set but is an empty string.
  53                 raise KeyError
  54         except KeyError:
  55             # NOTE: This is arguably an EnvironmentError, but that causes
  56             # problems with Python's interactive help.
  57             raise ImportError("Settings cannot be imported, because environment variable %s is undefined." % ENVIRONMENT_VARIABLE)
  58
  59         self._target = Settings(settings_module)
  60
  61     def configure(self, default_settings=global_settings, **options):
  62         """
  63         Called to manually configure the settings. The 'default_settings'
  64         parameter sets where to retrieve any unspecified values from (its
  65         argument must support attribute access (__getattr__)).
  66         """
  67         if self._target != None:
  68             raise RuntimeError, 'Settings already configured.'
  69         holder = UserSettingsHolder(default_settings)
  70         for name, value in options.items():
  71             setattr(holder, name, value)
  72         self._target = holder
  73
  74     def configured(self):
  75         """
  76         Returns True if the settings have already been configured.
  77         """
  78         return bool(self._target)
  79     configured = property(configured)
  80
  81 class Settings(object):
  82     def __init__(self, settings_module):
  83         # update this dict from global settings (but only for ALL_CAPS settings)
  84         for setting in dir(global_settings):
  85             if setting == setting.upper():
  86                 setattr(self, setting, getattr(global_settings, setting))
  87
  88         # store the settings module in case someone later cares
  89         self.SETTINGS_MODULE = settings_module
  90
  91         try:
  92             mod = __import__(self.SETTINGS_MODULE, {}, {}, [''])
  93         except ImportError, e:
  94             raise ImportError, "Could not import settings '%s' (Is it on sys.path? Does it have syntax errors?): %s" % (self.SETTINGS_MODULE, e)
  95
  96         # Settings that should be converted into tuples if they're mistakenly entered
  97         # as strings.
  98         tuple_settings = ("INSTALLED_APPS", "TEMPLATE_DIRS")
  99
 100         for setting in dir(mod):
 101             if setting == setting.upper():
 102                 setting_value = getattr(mod, setting)
 103                 if setting in tuple_settings and type(setting_value) == str:
 104                     setting_value = (setting_value,) # In case the user forgot the comma.
 105                 setattr(self, setting, setting_value)
 106
 107         # Expand entries in INSTALLED_APPS like "django.contrib.*" to a list
 108         # of all those apps.
 109         new_installed_apps = []
 110         for app in self.INSTALLED_APPS:
 111             if app.endswith('.*'):
 112                 appdir = os.path.dirname(__import__(app[:-2], {}, {}, ['']).__file__)
 113                 app_subdirs = os.listdir(appdir)
 114                 app_subdirs.sort()
 115                 for d in app_subdirs:
 116                     if d.isalpha() and os.path.isdir(os.path.join(appdir, d)):
 117                         new_installed_apps.append('%s.%s' % (app[:-2], d))
 118             else:
 119                 new_installed_apps.append(app)
 120         self.INSTALLED_APPS = new_installed_apps
 121
 122         if hasattr(time, 'tzset'):
 123             # Move the time zone info into os.environ. See ticket #2315 for why
 124             # we don't do this unconditionally (breaks Windows).
 125             os.environ['TZ'] = self.TIME_ZONE
 126             time.tzset()
 127
 128     def get_all_members(self):
 129         return dir(self)
 130
 131 class UserSettingsHolder(object):
 132     """
 133     Holder for user configured settings.
 134     """
 135     # SETTINGS_MODULE doesn't make much sense in the manually configured
 136     # (standalone) case.
 137     SETTINGS_MODULE = None
 138
 139     def __init__(self, default_settings):
 140         """
 141         Requests for configuration variables not in this class are satisfied
 142         from the module specified in default_settings (if possible).
 143         """
 144         self.default_settings = default_settings
 145
 146     def __getattr__(self, name):
 147         return getattr(self.default_settings, name)
 148
 149     def get_all_members(self):
 150         return dir(self) + dir(self.default_settings)
 151
 152 settings = LazySettings()
 153