1 from django.conf import settings

     2 from django.core.exceptions import ImproperlyConfigured

     3 

     4 _standard_context_processors = None

     5 

     6 class ContextPopException(Exception):

     7     "pop() has been called more times than push()"

     8     pass

     9 

    10 class Context(object):

    11     "A stack container for variable context"

    12     def __init__(self, dict_=None, autoescape=True):

    13         dict_ = dict_ or {}

    14         self.dicts = [dict_]

    15         self.autoescape = autoescape

    16 

    17     def __repr__(self):

    18         return repr(self.dicts)

    19 

    20     def __iter__(self):

    21         for d in self.dicts:

    22             yield d

    23 

    24     def push(self):

    25         d = {}

    26         self.dicts = [d] + self.dicts

    27         return d

    28 

    29     def pop(self):

    30         if len(self.dicts) == 1:

    31             raise ContextPopException

    32         return self.dicts.pop(0)

    33 

    34     def __setitem__(self, key, value):

    35         "Set a variable in the current context"

    36         self.dicts[0][key] = value

    37 

    38     def __getitem__(self, key):

    39         "Get a variable's value, starting at the current context and going upward"

    40         for d in self.dicts:

    41             if key in d:

    42                 return d[key]

    43         raise KeyError(key)

    44 

    45     def __delitem__(self, key):

    46         "Delete a variable from the current context"

    47         del self.dicts[0][key]

    48 

    49     def has_key(self, key):

    50         for d in self.dicts:

    51             if key in d:

    52                 return True

    53         return False

    54 

    55     __contains__ = has_key

    56 

    57     def get(self, key, otherwise=None):

    58         for d in self.dicts:

    59             if key in d:

    60                 return d[key]

    61         return otherwise

    62 

    63     def update(self, other_dict):

    64         "Like dict.update(). Pushes an entire dictionary's keys and values onto the context."

    65         self.dicts = [other_dict] + self.dicts

    66         return other_dict

    67 

    68 # This is a function rather than module-level procedural code because we only

    69 # want it to execute if somebody uses RequestContext.

    70 def get_standard_processors():

    71     global _standard_context_processors

    72     if _standard_context_processors is None:

    73         processors = []

    74         for path in settings.TEMPLATE_CONTEXT_PROCESSORS:

    75             i = path.rfind('.')

    76             module, attr = path[:i], path[i+1:]

    77             try:

    78                 mod = __import__(module, {}, {}, [attr])

    79             except ImportError, e:

    80                 raise ImproperlyConfigured('Error importing request processor module %s: "%s"' % (module, e))

    81             try:

    82                 func = getattr(mod, attr)

    83             except AttributeError:

    84                 raise ImproperlyConfigured('Module "%s" does not define a "%s" callable request processor' % (module, attr))

    85             processors.append(func)

    86         _standard_context_processors = tuple(processors)

    87     return _standard_context_processors

    88 

    89 class RequestContext(Context):

    90     """

    91     This subclass of template.Context automatically populates itself using

    92     the processors defined in TEMPLATE_CONTEXT_PROCESSORS.

    93     Additional processors can be specified as a list of callables

    94     using the "processors" keyword argument.

    95     """

    96     def __init__(self, request, dict=None, processors=None):

    97         Context.__init__(self, dict)

    98         if processors is None:

    99             processors = ()

   100         else:

   101             processors = tuple(processors)

   102         for processor in get_standard_processors() + processors:

   103             self.update(processor(request))