Refactor code to be more idiomatic and compatible with Python 3

Simplify some of the code and add dynamic accessesors to adapters.py
as indicated by the TODO.

lib/charm/openstack/adapters.py

@@ -15,10 +15,7 @@ class OpenStackRelationAdapter(object):
 
     def __init__(self, relation, accessors=None):
         self.relation = relation
-        if accessors:
-            self.accessors = accessors
-        else:
-            self.accessors = []
+        self.accessors = accessors or []
         self._setup_properties()
 
     @property
@@ -32,14 +29,17 @@ class OpenStackRelationAdapter(object):
         """
         Setup property based accessors for an interfaces
         auto accessors
+
+        Note that the accessor is dynamic as each access calls the underlying
+        getattr() for each property access.
         """
         self.accessors.extend(self.relation.auto_accessors)
         for field in self.accessors:
             meth_name = field.replace('-', '_')
-            # TODO: see if we can make this dynamic, rather
-            #       than making all calls on setup.
-            self.__dict__[meth_name] = getattr(self.relation,
-                                               meth_name)()
+            # Get the relation property dynamically
+            setattr(self.__class__,
+                    meth_name,
+                    property(lambda self: getattr(self.relation, meth_name)))
 
 
 class RabbitMQRelationAdapter(OpenStackRelationAdapter):
@@ -116,7 +116,8 @@ class DatabaseRelationAdapter(OpenStackRelationAdapter):
         if self.ssl_ca:
             uri = '{}?ssl_ca={}'.format(uri, self.ssl_ca)
             if self.ssl_cert:
-                uri = '{}&ssl_cert={}&ssl_key={}'.format(uri, self.ssl_cert,
+                uri = '{}&ssl_cert={}&ssl_key={}'.format(uri,
+                                                         self.ssl_cert,
                                                          self.ssl_key)
         return uri
 
@@ -135,7 +136,7 @@ class ConfigurationAdapter(object):
         _config = hookenv.config()
         for k, v in _config.items():
             k = k.replace('-', '_')
-            self.__dict__[k] = v
+            setattr(self, k, v)
 
 
 class OpenStackRelationAdapters(object):
@@ -172,16 +173,13 @@ class OpenStackRelationAdapters(object):
         self._relations = []
         for relation in relations:
             relation_name = relation.relation_name.replace('-', '_')
-            if relation_name in self._adapters:
-                self.__dict__[relation_name] = (
-                    self._adapters[relation_name](relation)
-                )
-            else:
-                self.__dict__[relation_name] = (
-                    OpenStackRelationAdapter(relation)
-                )
+            try:
+                relation_value = self._adapters[relation_name](relation)
+            except KeyError:
+                relation_value = OpenStackRelationAdapter(relation)
+            setattr(self, relation_name, relation_value)
             self._relations.append(relation_name)
-        self.__dict__['options'] = options()
+        self.options = options()
         self._relations.append('options')
 
     def __iter__(self):
@@ -189,4 +187,4 @@ class OpenStackRelationAdapters(object):
         Iterate over the relations presented to the charm.
         """
         for relation in self._relations:
-            yield relation, self.__dict__[relation]
+            yield relation, getattr(self, relation)

lib/charm/openstack/ip.py

@@ -16,7 +16,7 @@ PUBLIC = 'public'
 INTERNAL = 'int'
 ADMIN = 'admin'
 
-_address_map = {
+_ADDRESS_MAP = {
     PUBLIC: {
         'config': 'os-public-network',
         'fallback': 'public-address'
@@ -47,28 +47,28 @@ def canonical_url(endpoint_type=PUBLIC):
     address = resolve_address(endpoint_type)
     if is_ipv6(address):
         address = "[{}]".format(address)
-    return '%s://%s' % (scheme, address)
+    return "{0}://{1}".format(scheme, address)
 
 
 def resolve_address(endpoint_type=PUBLIC):
     resolved_address = None
     if is_clustered():
-        if config(_address_map[endpoint_type]['config']) is None:
+        if config(_ADDRESS_MAP[endpoint_type]['config']) is None:
             # Assume vip is simple and pass back directly
             resolved_address = config('vip')
         else:
             for vip in config('vip').split():
                 if is_address_in_network(
-                        config(_address_map[endpoint_type]['config']),
+                        config(_ADDRESS_MAP[endpoint_type]['config']),
                         vip):
                     resolved_address = vip
     else:
         if config('prefer-ipv6'):
             fallback_addr = get_ipv6_addr(exc_list=[config('vip')])[0]
         else:
-            fallback_addr = unit_get(_address_map[endpoint_type]['fallback'])
+            fallback_addr = unit_get(_ADDRESS_MAP[endpoint_type]['fallback'])
         resolved_address = get_address_in_network(
-            config(_address_map[endpoint_type]['config']), fallback_addr)
+            config(_ADDRESS_MAP[endpoint_type]['config']), fallback_addr)
 
     if resolved_address is None:
         raise ValueError('Unable to resolve a suitable IP address'