context.py

A MutableMapping subclass for use as a request-local context object.

 


            		
          

          

            
              

                
              

              
Imports

            		
            
              
from __future__ import unicode_literals

from collections import MutableMapping



            		
          

          

            
              

                
              

              
Mapping Class

            		
            
              


            		
          

          

            
              

                
              

              
An attribute access dictionary, of a kind.


This utility class is used to cooperatively construct the ApplicationContext (and subsequent RequestContext)
from the contributions of multiple extensions. The concept of "promotion to a class" is needed in order to enable
the use of descriptor protocol attributes; without promotion the protocol would not be utilized.

            		
            
              
class Context(MutableMapping):
	



            		
          

          

            
              

                
              

              
M-Morty! We're, belch, gonna have to go in deep, Morty!  Elbow deep!


Create a new subclass of Context which incorporates instance attributes and new descriptors.


This promotes an instance and its instance attributes up to being a class with class attributes, then
returns an instance of that class.

            		
            
              
	def _promote(self, name, instantiate=True):
		
		metaclass = type(self.__class__)
		contents = self.__dict__.copy()
		cls = metaclass(str(name), (self.__class__, ), contents)
		
		if instantiate:
			return cls()
		
		return cls
	



            		
          

          

            
              

                
              

              
Construct a new Context instance.


All keyword arguments are applied to the instance as attributes through direct assignment to __dict__.

            		
            
              
	def __init__(self, **kw):
		self.__dict__.update(kw)
		super(Context, self).__init__()
	



            		
          

          

            
              

                
              

              
Get a list of the public data attributes.

            		
            
              
	def __len__(self):
		return len([i for i in (set(dir(self)) - self._STANDARD_ATTRS) if i[0] != '_'])
	



            		
          

          

            
              

                
              

              
Iterate all valid (public) attributes/keys.

            		
            
              
	def __iter__(self):
		return (i for i in (set(dir(self)) - self._STANDARD_ATTRS) if i[0] != '_')
	



            		
          

          

            
              

                
              

              
Retrieve an attribute through dictionary access.

            		
            
              
	def __getitem__(self, name):
		try:
			return getattr(self, name)
		except AttributeError:
			pass
		



            		
          

          

            
              

                
              

              
We do this here to avoid Python 3's nested exception support.

            		
            
              
		raise KeyError(name)
	



            		
          

          

            
              

                
              

              
Assign an attribute through dictionary access.

            		
            
              
	def __setitem__(self, name, value):
		setattr(self, name, value)
	



            		
          

          

            
              

                
              

              
Delete an attribute through dictionary access.

            		
            
              
	def __delitem__(self, name):
		try:
			return delattr(self, name)
		except AttributeError:
			pass
		



            		
          

          

            
              

                
              

              
We do this here to avoid Python 3's nested exception support.

            		
            
              
		raise KeyError(name)



            		
          

          

            
              

                
              

              
We generally want to exclude "default object attributes" from the context's list of attributes.
 This auto-detects the basic set of them for exclusion from iteration in the above methods.

            		
            
              
Context._STANDARD_ATTRS = set(dir(Context()))