Source Code for Module lastfm.decorators

  1  #!/usr/bin/env python 
  2  """Module containting the decorators used in the package""" 
  3   
  4  __author__ = "Abhinav Sarkar <abhinav@abhinavsarkar.net>" 
  5  __version__ = "0.2" 
  6  __license__ = "GNU Lesser General Public License" 
  7   
  8 -def top_property(list_property_name): 
  9      """ 
 10      A decorator to return a property that returns the first value of list  
 11      attribute corresponding to the provided list property name. 
 12       
 13      For example, if the list property is top_albums, then the decorator returns 
 14      a property that returns the first (top most) album. 
 15       
 16      @param list_property_name: the name of the list property. Like 'top_albums'. 
 17      @type list_property_name:  L{str} 
 18       
 19      @return:                   a property that returns the first value of list attribute  
 20                                 corresponding to the provided list property name 
 21      @rtype:                    L{property} 
 22      """     
 23      def decorator(func): 
 24          def wrapper(ob): 
 25              top_list = getattr(ob, list_property_name) 
 26              return (len(top_list) and top_list[0] or None) 
 27          return property(fget = wrapper, doc = func.__doc__) 
 28      return decorator 
 29   
 30 -def cached_property(func): 
 31      """ 
 32      A decorator to cache the atrribute of the object. When called for the first time, 
 33      the value of the attribute is retrived and saved in an instance variable. Later 
 34      calls return the copy of the cached value, so that the original cached value 
 35      cannot be modified. 
 36       
 37      @param func:  the getter function of the attribute 
 38      @type func:   C{function} 
 39       
 40      @return:      a property that wraps the getter function of the attribute 
 41      @rtype:       L{property} 
 42      """ 
 43      func_name = func.func_code.co_name 
 44      attribute_name = "_%s" % func_name 
 45   
 46      def wrapper(ob): 
 47          cache_attribute = getattr(ob, attribute_name, None) 
 48          if cache_attribute is None: 
 49              cache_attribute = func(ob) 
 50              setattr(ob, attribute_name, cache_attribute) 
 51          try: 
 52              cp = copy.copy(cache_attribute) 
 53              return cp 
 54          except LastfmError: 
 55              return cache_attribute 
 56   
 57      return property(fget = wrapper, doc = func.__doc__) 
 58   
 59 -def authenticate(func): 
 60      """ 
 61      A decorator to check if the current user is authenticated or not. Used only 
 62      on the functions that need authentication. If not authenticated then an 
 63      exception is raised. 
 64       
 65      @param func:    a function that needs to be authentication, for being called 
 66      @type func:     C{function} 
 67       
 68      @return:        a function that wraps the original function 
 69      @rtype:         C{function} 
 70       
 71      @raise AuthenticationFailedError: If the user is not authenticated, then an 
 72                                        exception is raised. 
 73      """ 
 74      def wrapper(self, *args, **kwargs): 
 75          from lastfm.user import User, Api 
 76          username = None 
 77          if isinstance(self, User): 
 78              username = self.name 
 79              if self.authenticated: 
 80                 return func(self, *args, **kwargs) 
 81          elif hasattr(self, 'user'): 
 82              username = self.user.name 
 83              if self.user.authenticated: 
 84                 return func(self, *args, **kwargs) 
 85          elif hasattr(self, '_subject') and isinstance(self._subject, User): 
 86              username = self._subject.name 
 87              if self._subject.authenticated: 
 88                  return func(self, *args, **kwargs) 
 89          elif hasattr(self, '_api') and isinstance(self._api, Api): 
 90              try: 
 91                  user = self._api.get_authenticated_user() 
 92                  username = user.name 
 93                  return func(self, *args, **kwargs) 
 94              except AuthenticationFailedError: 
 95                  pass 
 96          raise AuthenticationFailedError( 
 97              "user '%s' does not have permissions to access the service" % username) 
 98      return wrapper 
 99   
100  import copy 
101  from lastfm.error import LastfmError, AuthenticationFailedError 
102