diff --git a/examples/custom_stanzas/stanza.py b/examples/custom_stanzas/stanza.py
index b2c6f766..17b7c7de 100644
--- a/examples/custom_stanzas/stanza.py
+++ b/examples/custom_stanzas/stanza.py
@@ -41,7 +41,7 @@ class Action(ElementBase):
     #:     del action['status']
     #:
     #: to set, get, or remove its values.
-    interfaces = set(('method', 'param', 'status'))
+    interfaces = {'method', 'param', 'status'}
 
     #: By default, values in the `interfaces` set are mapped to
     #: attribute values. This can be changed such that an interface
diff --git a/slixmpp/features/feature_bind/stanza.py b/slixmpp/features/feature_bind/stanza.py
index b9ecd97c..96c3e757 100644
--- a/slixmpp/features/feature_bind/stanza.py
+++ b/slixmpp/features/feature_bind/stanza.py
@@ -16,6 +16,6 @@ class Bind(ElementBase):
 
     name = 'bind'
     namespace = 'urn:ietf:params:xml:ns:xmpp-bind'
-    interfaces = set(('resource', 'jid'))
+    interfaces = {'resource', 'jid'}
     sub_interfaces = interfaces
     plugin_attrib = 'bind'
diff --git a/slixmpp/features/feature_mechanisms/stanza/auth.py b/slixmpp/features/feature_mechanisms/stanza/auth.py
index c32069ec..e024ef22 100644
--- a/slixmpp/features/feature_mechanisms/stanza/auth.py
+++ b/slixmpp/features/feature_mechanisms/stanza/auth.py
@@ -19,7 +19,7 @@ class Auth(StanzaBase):
 
     name = 'auth'
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
-    interfaces = set(('mechanism', 'value'))
+    interfaces = {'mechanism', 'value'}
     plugin_attrib = name
 
     #: Some SASL mechs require sending values as is,
diff --git a/slixmpp/features/feature_mechanisms/stanza/failure.py b/slixmpp/features/feature_mechanisms/stanza/failure.py
index 29f0a343..b4428fcc 100644
--- a/slixmpp/features/feature_mechanisms/stanza/failure.py
+++ b/slixmpp/features/feature_mechanisms/stanza/failure.py
@@ -16,7 +16,7 @@ class Failure(StanzaBase):
 
     name = 'failure'
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
-    interfaces = set(('condition', 'text'))
+    interfaces = {'condition', 'text'}
     plugin_attrib = name
     sub_interfaces = {'text'}
     conditions = set(('aborted', 'account-disabled', 'credentials-expired',
diff --git a/slixmpp/features/feature_mechanisms/stanza/mechanisms.py b/slixmpp/features/feature_mechanisms/stanza/mechanisms.py
index 064b8d1f..4ff15678 100644
--- a/slixmpp/features/feature_mechanisms/stanza/mechanisms.py
+++ b/slixmpp/features/feature_mechanisms/stanza/mechanisms.py
@@ -16,7 +16,7 @@ class Mechanisms(ElementBase):
 
     name = 'mechanisms'
     namespace = 'urn:ietf:params:xml:ns:xmpp-sasl'
-    interfaces = set(('mechanisms', 'required'))
+    interfaces = {'mechanisms', 'required'}
     plugin_attrib = name
     is_extension = True
 
diff --git a/slixmpp/plugins/gmail_notify.py b/slixmpp/plugins/gmail_notify.py
index f4cf188c..2a85e17f 100644
--- a/slixmpp/plugins/gmail_notify.py
+++ b/slixmpp/plugins/gmail_notify.py
@@ -21,7 +21,7 @@ class GmailQuery(ElementBase):
     namespace = 'google:mail:notify'
     name = 'query'
     plugin_attrib = 'gmail'
-    interfaces = set(('newer-than-time', 'newer-than-tid', 'q', 'search'))
+    interfaces = {'newer-than-time', 'newer-than-tid', 'q', 'search'}
 
     def get_search(self):
         return self['q']
@@ -60,7 +60,7 @@ class MailThread(ElementBase):
     plugin_attrib = 'thread'
     interfaces = set(('tid', 'participation', 'messages', 'date',
                       'senders', 'url', 'labels', 'subject', 'snippet'))
-    sub_interfaces = set(('labels', 'subject', 'snippet'))
+    sub_interfaces = {'labels', 'subject', 'snippet'}
 
     def get_senders(self):
         senders = []
@@ -75,7 +75,7 @@ class MailSender(ElementBase):
     namespace = 'google:mail:notify'
     name = 'sender'
     plugin_attrib = 'sender'
-    interfaces = set(('address', 'name', 'originator', 'unread'))
+    interfaces = {'address', 'name', 'originator', 'unread'}
 
     def get_originator(self):
         return self.xml.attrib.get('originator', '0') == '1'
diff --git a/slixmpp/plugins/xep_0004/stanza/field.py b/slixmpp/plugins/xep_0004/stanza/field.py
index 2bcc823a..2eebbe6f 100644
--- a/slixmpp/plugins/xep_0004/stanza/field.py
+++ b/slixmpp/plugins/xep_0004/stanza/field.py
@@ -24,9 +24,9 @@ class FormField(ElementBase):
                        'jid-single', 'list-multi', 'list-single',
                        'text-multi', 'text-private', 'text-single'))
 
-    true_values = set((True, '1', 'true'))
-    option_types = set(('list-multi', 'list-single'))
-    multi_line_types = set(('hidden', 'text-multi'))
+    true_values = {True, '1', 'true'}
+    option_types = {'list-multi', 'list-single'}
+    multi_line_types = {'hidden', 'text-multi'}
     multi_value_types = set(('hidden', 'jid-multi',
                              'list-multi', 'text-multi'))
 
@@ -164,7 +164,7 @@ class FieldOption(ElementBase):
     namespace = 'jabber:x:data'
     name = 'option'
     plugin_attrib = 'option'
-    interfaces = set(('label', 'value'))
+    interfaces = {'label', 'value'}
     sub_interfaces = {'value'}
     plugin_multi_attrib = 'options'
 
diff --git a/slixmpp/plugins/xep_0004/stanza/form.py b/slixmpp/plugins/xep_0004/stanza/form.py
index 52b18f81..0ae22098 100644
--- a/slixmpp/plugins/xep_0004/stanza/form.py
+++ b/slixmpp/plugins/xep_0004/stanza/form.py
@@ -25,7 +25,7 @@ class Form(ElementBase):
     plugin_attrib = 'form'
     interfaces = OrderedSet(('instructions', 'reported', 'title', 'type', 'items', ))
     sub_interfaces = {'title'}
-    form_types = set(('cancel', 'form', 'result', 'submit'))
+    form_types = {'cancel', 'form', 'result', 'submit'}
 
     def __init__(self, *args, **kwargs):
         title = None
diff --git a/slixmpp/plugins/xep_0009/stanza/RPC.py b/slixmpp/plugins/xep_0009/stanza/RPC.py
index 3abab8fc..f8cec481 100644
--- a/slixmpp/plugins/xep_0009/stanza/RPC.py
+++ b/slixmpp/plugins/xep_0009/stanza/RPC.py
@@ -14,8 +14,8 @@ class RPCQuery(ElementBase):
     name = 'query'
     namespace = 'jabber:iq:rpc'
     plugin_attrib = 'rpc_query'
-    interfaces = set(())
-    subinterfaces = set(())
+    interfaces = {}
+    subinterfaces = {}
     plugin_attrib_map = {}
     plugin_tag_map = {}
 
@@ -24,8 +24,8 @@ class MethodCall(ElementBase):
     name = 'methodCall'
     namespace = 'jabber:iq:rpc'
     plugin_attrib = 'method_call'
-    interfaces = set(('method_name', 'params'))
-    subinterfaces = set(())
+    interfaces = {'method_name', 'params'}
+    subinterfaces = {}
     plugin_attrib_map = {}
     plugin_tag_map = {}
 
@@ -46,8 +46,8 @@ class MethodResponse(ElementBase):
     name = 'methodResponse'
     namespace = 'jabber:iq:rpc'
     plugin_attrib = 'method_response'
-    interfaces = set(('params', 'fault'))
-    subinterfaces = set(())
+    interfaces = {'params', 'fault'}
+    subinterfaces = {}
     plugin_attrib_map = {}
     plugin_tag_map = {}
 
diff --git a/slixmpp/plugins/xep_0012/stanza.py b/slixmpp/plugins/xep_0012/stanza.py
index bd539a2d..16ca6fcf 100644
--- a/slixmpp/plugins/xep_0012/stanza.py
+++ b/slixmpp/plugins/xep_0012/stanza.py
@@ -14,7 +14,7 @@ class LastActivity(ElementBase):
     name = 'query'
     namespace = 'jabber:iq:last'
     plugin_attrib = 'last_activity'
-    interfaces = set(('seconds', 'status'))
+    interfaces = {'seconds', 'status'}
 
     def get_seconds(self):
         return int(self._get_attr('seconds'))
diff --git a/slixmpp/plugins/xep_0030/stanza/info.py b/slixmpp/plugins/xep_0030/stanza/info.py
index a09c85a8..7102d529 100644
--- a/slixmpp/plugins/xep_0030/stanza/info.py
+++ b/slixmpp/plugins/xep_0030/stanza/info.py
@@ -71,7 +71,7 @@ class DiscoInfo(ElementBase):
     name = 'query'
     namespace = 'http://jabber.org/protocol/disco#info'
     plugin_attrib = 'disco_info'
-    interfaces = set(('node', 'features', 'identities'))
+    interfaces = {'node', 'features', 'identities'}
     lang_interfaces = {'identities'}
 
     # Cache identities and features
diff --git a/slixmpp/plugins/xep_0030/stanza/items.py b/slixmpp/plugins/xep_0030/stanza/items.py
index 314ab9b3..a59d9114 100644
--- a/slixmpp/plugins/xep_0030/stanza/items.py
+++ b/slixmpp/plugins/xep_0030/stanza/items.py
@@ -45,7 +45,7 @@ class DiscoItems(ElementBase):
     name = 'query'
     namespace = 'http://jabber.org/protocol/disco#items'
     plugin_attrib = 'disco_items'
-    interfaces = set(('node', 'items'))
+    interfaces = {'node', 'items'}
 
     # Cache items
     _items = set()
@@ -138,7 +138,7 @@ class DiscoItem(ElementBase):
     name = 'item'
     namespace = 'http://jabber.org/protocol/disco#items'
     plugin_attrib = name
-    interfaces = set(('jid', 'node', 'name'))
+    interfaces = {'jid', 'node', 'name'}
 
     def get_node(self):
         """Return the item's node name or ``None``."""
diff --git a/slixmpp/plugins/xep_0033/stanza.py b/slixmpp/plugins/xep_0033/stanza.py
index 50c7b6db..d2a67de1 100644
--- a/slixmpp/plugins/xep_0033/stanza.py
+++ b/slixmpp/plugins/xep_0033/stanza.py
@@ -39,7 +39,7 @@ class Address(ElementBase):
     plugin_attrib = 'address'
     interfaces = set(['type', 'jid', 'node', 'uri', 'desc', 'delivered'])
 
-    address_types = set(('bcc', 'cc', 'noreply', 'replyroom', 'replyto', 'to'))
+    address_types = {'bcc', 'cc', 'noreply', 'replyroom', 'replyto', 'to'}
 
     def get_jid(self):
         return JID(self._get_attr('jid'))
diff --git a/slixmpp/plugins/xep_0045.py b/slixmpp/plugins/xep_0045.py
index 942ba22a..ce4631ef 100644
--- a/slixmpp/plugins/xep_0045.py
+++ b/slixmpp/plugins/xep_0045.py
@@ -25,9 +25,9 @@ class MUCPresence(ElementBase):
     name = 'x'
     namespace = 'http://jabber.org/protocol/muc#user'
     plugin_attrib = 'muc'
-    interfaces = set(('affiliation', 'role', 'jid', 'nick', 'room'))
-    affiliations = set(('', ))
-    roles = set(('', ))
+    interfaces = {'affiliation', 'role', 'jid', 'nick', 'room'}
+    affiliations = {'', }
+    roles = {'', }
 
     def get_xml_item(self):
         item = self.xml.find('{http://jabber.org/protocol/muc#user}item')
diff --git a/slixmpp/plugins/xep_0047/stanza.py b/slixmpp/plugins/xep_0047/stanza.py
index 7f8ff0ba..91f17c1c 100644
--- a/slixmpp/plugins/xep_0047/stanza.py
+++ b/slixmpp/plugins/xep_0047/stanza.py
@@ -21,7 +21,7 @@ class Open(ElementBase):
     name = 'open'
     namespace = 'http://jabber.org/protocol/ibb'
     plugin_attrib = 'ibb_open'
-    interfaces = set(('block_size', 'sid', 'stanza'))
+    interfaces = {'block_size', 'sid', 'stanza'}
 
     def get_block_size(self):
         return int(self._get_attr('block-size', '0'))
@@ -37,7 +37,7 @@ class Data(ElementBase):
     name = 'data'
     namespace = 'http://jabber.org/protocol/ibb'
     plugin_attrib = 'ibb_data'
-    interfaces = set(('seq', 'sid', 'data'))
+    interfaces = {'seq', 'sid', 'data'}
     sub_interfaces = set(['data'])
 
     def get_seq(self):
diff --git a/slixmpp/plugins/xep_0050/stanza.py b/slixmpp/plugins/xep_0050/stanza.py
index 107135f4..d512425d 100644
--- a/slixmpp/plugins/xep_0050/stanza.py
+++ b/slixmpp/plugins/xep_0050/stanza.py
@@ -74,9 +74,9 @@ class Command(ElementBase):
     plugin_attrib = 'command'
     interfaces = set(('action', 'sessionid', 'node',
                       'status', 'actions', 'notes'))
-    actions = set(('cancel', 'complete', 'execute', 'next', 'prev'))
-    statuses = set(('canceled', 'completed', 'executing'))
-    next_actions = set(('prev', 'next', 'complete'))
+    actions = {'cancel', 'complete', 'execute', 'next', 'prev'}
+    statuses = {'canceled', 'completed', 'executing'}
+    next_actions = {'prev', 'next', 'complete'}
 
     def get_action(self):
         """
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub.py b/slixmpp/plugins/xep_0060/stanza/pubsub.py
index 841e69d2..210bce08 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub.py
@@ -30,7 +30,7 @@ class Affiliation(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'affiliation'
     plugin_attrib = name
-    interfaces = set(('node', 'affiliation', 'jid'))
+    interfaces = {'node', 'affiliation', 'jid'}
 
     def set_jid(self, value):
         self._set_attr('jid', str(value))
@@ -43,7 +43,7 @@ class Subscription(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'subscription'
     plugin_attrib = name
-    interfaces = set(('jid', 'node', 'subscription', 'subid'))
+    interfaces = {'jid', 'node', 'subscription', 'subid'}
 
     def set_jid(self, value):
         self._set_attr('jid', str(value))
@@ -70,7 +70,7 @@ class Item(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'item'
     plugin_attrib = name
-    interfaces = set(('id', 'payload'))
+    interfaces = {'id', 'payload'}
 
     def set_payload(self, value):
         del self['payload']
@@ -95,7 +95,7 @@ class Items(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'items'
     plugin_attrib = name
-    interfaces = set(('node', 'max_items'))
+    interfaces = {'node', 'max_items'}
 
     def set_max_items(self, value):
         self._set_attr('max_items', str(value))
@@ -112,7 +112,7 @@ class Default(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'default'
     plugin_attrib = name
-    interfaces = set(('node', 'type'))
+    interfaces = {'node', 'type'}
 
     def get_type(self):
         t = self._get_attr('type')
@@ -132,7 +132,7 @@ class Retract(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'retract'
     plugin_attrib = name
-    interfaces = set(('node', 'notify'))
+    interfaces = {'node', 'notify'}
 
     def get_notify(self):
         notify = self._get_attr('notify')
@@ -156,7 +156,7 @@ class Unsubscribe(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'unsubscribe'
     plugin_attrib = name
-    interfaces = set(('node', 'jid', 'subid'))
+    interfaces = {'node', 'jid', 'subid'}
 
     def set_jid(self, value):
         self._set_attr('jid', str(value))
@@ -169,7 +169,7 @@ class Subscribe(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'subscribe'
     plugin_attrib = name
-    interfaces = set(('node', 'jid'))
+    interfaces = {'node', 'jid'}
 
     def set_jid(self, value):
         self._set_attr('jid', str(value))
@@ -182,7 +182,7 @@ class Configure(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'configure'
     plugin_attrib = name
-    interfaces = set(('node', 'type'))
+    interfaces = {'node', 'type'}
 
     def getType(self):
         t = self._get_attr('type')
@@ -195,7 +195,7 @@ class Options(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub'
     name = 'options'
     plugin_attrib = name
-    interfaces = set(('jid', 'node', 'options'))
+    interfaces = {'jid', 'node', 'options'}
 
     def __init__(self, *args, **kwargs):
         ElementBase.__init__(self, *args, **kwargs)
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub_errors.py b/slixmpp/plugins/xep_0060/stanza/pubsub_errors.py
index 3e728009..7786c854 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub_errors.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub_errors.py
@@ -13,7 +13,7 @@ from slixmpp.xmlstream import ElementBase, ET, register_stanza_plugin
 class PubsubErrorCondition(ElementBase):
 
     plugin_attrib = 'pubsub'
-    interfaces = set(('condition', 'unsupported'))
+    interfaces = {'condition', 'unsupported'}
     plugin_attrib_map = {}
     plugin_tag_map = {}
     conditions = set(('closed-node', 'configuration-required', 'invalid-jid',
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub_event.py b/slixmpp/plugins/xep_0060/stanza/pubsub_event.py
index b2b53d3d..e46ad408 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub_event.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub_event.py
@@ -25,7 +25,7 @@ class EventItem(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'item'
     plugin_attrib = name
-    interfaces = set(('id', 'payload', 'node', 'publisher'))
+    interfaces = {'id', 'payload', 'node', 'publisher'}
 
     def set_payload(self, value):
         self.xml.append(value)
@@ -93,7 +93,7 @@ class EventDelete(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'delete'
     plugin_attrib = name
-    interfaces = set(('node', 'redirect'))
+    interfaces = {'node', 'redirect'}
 
     def set_redirect(self, uri):
         del self['redirect']
@@ -117,7 +117,7 @@ class EventSubscription(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#event'
     name = 'subscription'
     plugin_attrib = name
-    interfaces = set(('node', 'expiry', 'jid', 'subid', 'subscription'))
+    interfaces = {'node', 'expiry', 'jid', 'subid', 'subscription'}
 
     def get_expiry(self):
         expiry = self._get_attr('expiry')
diff --git a/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py b/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py
index bcb96149..850df8cf 100644
--- a/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py
+++ b/slixmpp/plugins/xep_0060/stanza/pubsub_owner.py
@@ -25,7 +25,7 @@ class DefaultConfig(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     name = 'default'
     plugin_attrib = name
-    interfaces = set(('node', 'config'))
+    interfaces = {'node', 'config'}
 
     def __init__(self, *args, **kwargs):
         ElementBase.__init__(self, *args, **kwargs)
@@ -51,7 +51,7 @@ class OwnerAffiliations(Affiliations):
 
 class OwnerAffiliation(Affiliation):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
-    interfaces = set(('affiliation', 'jid'))
+    interfaces = {'affiliation', 'jid'}
 
 
 class OwnerConfigure(Configure):
@@ -84,7 +84,7 @@ class OwnerRedirect(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     name = 'redirect'
     plugin_attrib = name
-    interfaces = set(('node', 'jid'))
+    interfaces = {'node', 'jid'}
 
     def set_jid(self, value):
         self._set_attr('jid', str(value))
@@ -109,7 +109,7 @@ class OwnerSubscription(ElementBase):
     namespace = 'http://jabber.org/protocol/pubsub#owner'
     name = 'subscription'
     plugin_attrib = name
-    interfaces = set(('jid', 'subscription'))
+    interfaces = {'jid', 'subscription'}
 
     def set_jid(self, value):
         self._set_attr('jid', str(value))
diff --git a/slixmpp/plugins/xep_0066/stanza.py b/slixmpp/plugins/xep_0066/stanza.py
index e1da5bdd..55707b99 100644
--- a/slixmpp/plugins/xep_0066/stanza.py
+++ b/slixmpp/plugins/xep_0066/stanza.py
@@ -17,8 +17,8 @@ class OOBTransfer(ElementBase):
     name = 'query'
     namespace = 'jabber:iq:oob'
     plugin_attrib = 'oob_transfer'
-    interfaces = set(('url', 'desc', 'sid'))
-    sub_interfaces = set(('url', 'desc'))
+    interfaces = {'url', 'desc', 'sid'}
+    sub_interfaces = {'url', 'desc'}
 
 
 class OOB(ElementBase):
@@ -29,5 +29,5 @@ class OOB(ElementBase):
     name = 'x'
     namespace = 'jabber:x:oob'
     plugin_attrib = 'oob'
-    interfaces = set(('url', 'desc'))
+    interfaces = {'url', 'desc'}
     sub_interfaces = interfaces
diff --git a/slixmpp/plugins/xep_0078/stanza.py b/slixmpp/plugins/xep_0078/stanza.py
index 7dc9401d..2a9ba510 100644
--- a/slixmpp/plugins/xep_0078/stanza.py
+++ b/slixmpp/plugins/xep_0078/stanza.py
@@ -13,8 +13,8 @@ class IqAuth(ElementBase):
     namespace = 'jabber:iq:auth'
     name = 'query'
     plugin_attrib = 'auth'
-    interfaces = set(('fields', 'username', 'password', 'resource', 'digest'))
-    sub_interfaces = set(('username', 'password', 'resource', 'digest'))
+    interfaces = {'fields', 'username', 'password', 'resource', 'digest'}
+    sub_interfaces = {'username', 'password', 'resource', 'digest'}
     plugin_tag_map = {}
     plugin_attrib_map = {}
 
diff --git a/slixmpp/plugins/xep_0085/stanza.py b/slixmpp/plugins/xep_0085/stanza.py
index f5048f45..d0987308 100644
--- a/slixmpp/plugins/xep_0085/stanza.py
+++ b/slixmpp/plugins/xep_0085/stanza.py
@@ -41,7 +41,7 @@ class ChatState(ElementBase):
     sub_interfaces = interfaces
     is_extension = True
 
-    states = set(('active', 'composing', 'gone', 'inactive', 'paused'))
+    states = {'active', 'composing', 'gone', 'inactive', 'paused'}
 
     def setup(self, xml=None):
         self.xml = ET.Element('')
diff --git a/slixmpp/plugins/xep_0091/stanza.py b/slixmpp/plugins/xep_0091/stanza.py
index ac6457e6..0ce2acda 100644
--- a/slixmpp/plugins/xep_0091/stanza.py
+++ b/slixmpp/plugins/xep_0091/stanza.py
@@ -18,7 +18,7 @@ class LegacyDelay(ElementBase):
     name = 'x'
     namespace = 'jabber:x:delay'
     plugin_attrib = 'legacy_delay'
-    interfaces = set(('from', 'stamp', 'text'))
+    interfaces = {'from', 'stamp', 'text'}
 
     def get_from(self):
         from_ = self._get_attr('from')
diff --git a/slixmpp/plugins/xep_0092/stanza.py b/slixmpp/plugins/xep_0092/stanza.py
index 04097a8b..e76a041e 100644
--- a/slixmpp/plugins/xep_0092/stanza.py
+++ b/slixmpp/plugins/xep_0092/stanza.py
@@ -38,5 +38,5 @@ class Version(ElementBase):
     name = 'query'
     namespace = 'jabber:iq:version'
     plugin_attrib = 'software_version'
-    interfaces = set(('name', 'version', 'os'))
+    interfaces = {'name', 'version', 'os'}
     sub_interfaces = interfaces
diff --git a/slixmpp/plugins/xep_0115/stanza.py b/slixmpp/plugins/xep_0115/stanza.py
index 36fb173c..1811307f 100644
--- a/slixmpp/plugins/xep_0115/stanza.py
+++ b/slixmpp/plugins/xep_0115/stanza.py
@@ -16,4 +16,4 @@ class Capabilities(ElementBase):
     namespace = 'http://jabber.org/protocol/caps'
     name = 'c'
     plugin_attrib = 'caps'
-    interfaces = set(('hash', 'node', 'ver', 'ext'))
+    interfaces = {'hash', 'node', 'ver', 'ext'}
diff --git a/slixmpp/plugins/xep_0202/stanza.py b/slixmpp/plugins/xep_0202/stanza.py
index c855663b..d97b2fb2 100644
--- a/slixmpp/plugins/xep_0202/stanza.py
+++ b/slixmpp/plugins/xep_0202/stanza.py
@@ -48,7 +48,7 @@ class EntityTime(ElementBase):
     name = 'time'
     namespace = 'urn:xmpp:time'
     plugin_attrib = 'entity_time'
-    interfaces = set(('tzo', 'utc', 'time'))
+    interfaces = {'tzo', 'utc', 'time'}
     sub_interfaces = interfaces
 
     def set_time(self, value):
diff --git a/slixmpp/plugins/xep_0203/stanza.py b/slixmpp/plugins/xep_0203/stanza.py
index de907c69..5daed864 100644
--- a/slixmpp/plugins/xep_0203/stanza.py
+++ b/slixmpp/plugins/xep_0203/stanza.py
@@ -18,7 +18,7 @@ class Delay(ElementBase):
     name = 'delay'
     namespace = 'urn:xmpp:delay'
     plugin_attrib = 'delay'
-    interfaces = set(('from', 'stamp', 'text'))
+    interfaces = {'from', 'stamp', 'text'}
 
     def get_from(self):
         from_ = self._get_attr('from')
diff --git a/slixmpp/plugins/xep_0231/stanza.py b/slixmpp/plugins/xep_0231/stanza.py
index b3b96eff..3de99aac 100644
--- a/slixmpp/plugins/xep_0231/stanza.py
+++ b/slixmpp/plugins/xep_0231/stanza.py
@@ -18,7 +18,7 @@ class BitsOfBinary(ElementBase):
     name = 'data'
     namespace = 'urn:xmpp:bob'
     plugin_attrib = 'bob'
-    interfaces = set(('cid', 'max_age', 'type', 'data'))
+    interfaces = {'cid', 'max_age', 'type', 'data'}
 
     def get_max_age(self):
         return int(self._get_attr('max-age'))
diff --git a/slixmpp/stanza/atom.py b/slixmpp/stanza/atom.py
index ccded724..c7192dd8 100644
--- a/slixmpp/stanza/atom.py
+++ b/slixmpp/stanza/atom.py
@@ -21,7 +21,7 @@ class AtomEntry(ElementBase):
     namespace = 'http://www.w3.org/2005/Atom'
     name = 'entry'
     plugin_attrib = 'entry'
-    interfaces = set(('title', 'summary', 'id', 'published', 'updated'))
+    interfaces = {'title', 'summary', 'id', 'published', 'updated'}
     sub_interfaces = set(('title', 'summary', 'id', 'published',
                           'updated'))
 
@@ -37,7 +37,7 @@ class AtomAuthor(ElementBase):
 
     name = 'author'
     plugin_attrib = 'author'
-    interfaces = set(('name', 'uri'))
-    sub_interfaces = set(('name', 'uri'))
+    interfaces = {'name', 'uri'}
+    sub_interfaces = {'name', 'uri'}
 
 register_stanza_plugin(AtomEntry, AtomAuthor)
diff --git a/slixmpp/stanza/error.py b/slixmpp/stanza/error.py
index 1499c652..145aaa24 100644
--- a/slixmpp/stanza/error.py
+++ b/slixmpp/stanza/error.py
@@ -66,7 +66,7 @@ class Error(ElementBase):
                       'service-unavailable', 'subscription-required',
                       'undefined-condition', 'unexpected-request'))
     condition_ns = 'urn:ietf:params:xml:ns:xmpp-stanzas'
-    types = set(('cancel', 'continue', 'modify', 'auth', 'wait'))
+    types = {'cancel', 'continue', 'modify', 'auth', 'wait'}
 
     def setup(self, xml=None):
         """
diff --git a/slixmpp/stanza/iq.py b/slixmpp/stanza/iq.py
index a64dfa7f..af7e3109 100644
--- a/slixmpp/stanza/iq.py
+++ b/slixmpp/stanza/iq.py
@@ -57,8 +57,8 @@ class Iq(RootStanza):
 
     namespace = 'jabber:client'
     name = 'iq'
-    interfaces = set(('type', 'to', 'from', 'id', 'query'))
-    types = set(('get', 'result', 'set', 'error'))
+    interfaces = {'type', 'to', 'from', 'id', 'query'}
+    types = {'get', 'result', 'set', 'error'}
     plugin_attrib = name
 
     def __init__(self, *args, **kwargs):
diff --git a/slixmpp/stanza/roster.py b/slixmpp/stanza/roster.py
index c017c33f..f846d595 100644
--- a/slixmpp/stanza/roster.py
+++ b/slixmpp/stanza/roster.py
@@ -36,7 +36,7 @@ class Roster(ElementBase):
     namespace = 'jabber:iq:roster'
     name = 'query'
     plugin_attrib = 'roster'
-    interfaces = set(('items', 'ver'))
+    interfaces = {'items', 'ver'}
 
     def get_ver(self):
         """
diff --git a/slixmpp/stanza/stream_error.py b/slixmpp/stanza/stream_error.py
index d8b8bb5a..1b5cceb2 100644
--- a/slixmpp/stanza/stream_error.py
+++ b/slixmpp/stanza/stream_error.py
@@ -54,7 +54,7 @@ class StreamError(Error, StanzaBase):
     """
 
     namespace = 'http://etherx.jabber.org/streams'
-    interfaces = set(('condition', 'text', 'see_other_host'))
+    interfaces = {'condition', 'text', 'see_other_host'}
     conditions = set((
         'bad-format', 'bad-namespace-prefix', 'conflict',
         'connection-timeout', 'host-gone', 'host-unknown',
diff --git a/slixmpp/stanza/stream_features.py b/slixmpp/stanza/stream_features.py
index 05788771..70d0ccca 100644
--- a/slixmpp/stanza/stream_features.py
+++ b/slixmpp/stanza/stream_features.py
@@ -17,7 +17,7 @@ class StreamFeatures(StanzaBase):
 
     name = 'features'
     namespace = 'http://etherx.jabber.org/streams'
-    interfaces = set(('features', 'required', 'optional'))
+    interfaces = {'features', 'required', 'optional'}
     sub_interfaces = interfaces
     plugin_tag_map = {}
     plugin_attrib_map = {}
diff --git a/slixmpp/xmlstream/stanzabase.py b/slixmpp/xmlstream/stanzabase.py
index 306fdb2e..1108adfb 100644
--- a/slixmpp/xmlstream/stanzabase.py
+++ b/slixmpp/xmlstream/stanzabase.py
@@ -212,7 +212,7 @@ class ElementBase(object):
         >>> class Message(ElementBase):
         ...     name = "message"
         ...     namespace = "jabber:client"
-        ...     interfaces = set(('to', 'from', 'type', 'body'))
+        ...     interfaces = {'to', 'from', 'type', 'body'}
         ...     sub_interfaces = {'body'}
 
     The resulting Message stanza's contents may be accessed as so::
@@ -239,7 +239,7 @@ class ElementBase(object):
         >>> class MessagePlugin(ElementBase):
         ...     name = "custom_plugin"
         ...     namespace = "custom"
-        ...     interfaces = set(('useful_thing', 'custom'))
+        ...     interfaces = {'useful_thing', 'custom'}
         ...     plugin_attrib = "custom"
 
     The plugin stanza class must be associated with its intended
@@ -311,7 +311,7 @@ class ElementBase(object):
     #: manipulating the underlying XML object. This set may be augmented
     #: with the :attr:`plugin_attrib` value of any registered
     #: stanza plugins.
-    interfaces = set(('type', 'to', 'from', 'id', 'payload'))
+    interfaces = {'type', 'to', 'from', 'id', 'payload'}
 
     #: A subset of :attr:`interfaces` which maps interfaces to direct
     #: subelements of the underlying XML object. Using this set, the text
@@ -1385,10 +1385,10 @@ class StanzaBase(ElementBase):
     #: There is a small set of attributes which apply to all XMPP stanzas:
     #: the stanza type, the to and from JIDs, the stanza ID, and, especially
     #: in the case of an Iq stanza, a payload.
-    interfaces = set(('type', 'to', 'from', 'id', 'payload'))
+    interfaces = {'type', 'to', 'from', 'id', 'payload'}
 
     #: A basic set of allowed values for the ``'type'`` interface.
-    types = set(('get', 'set', 'error', None, 'unavailable', 'normal', 'chat'))
+    types = {'get', 'set', 'error', None, 'unavailable', 'normal', 'chat'}
 
     def __init__(self, stream=None, xml=None, stype=None,
                  sto=None, sfrom=None, sid=None, parent=None):
diff --git a/tests/test_stanza_element.py b/tests/test_stanza_element.py
index 7b6c5561..26cc2438 100644
--- a/tests/test_stanza_element.py
+++ b/tests/test_stanza_element.py
@@ -43,18 +43,18 @@ class TestElementBase(SlixTest):
         class TestStanzaPlugin(ElementBase):
             name = "foo2"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
             plugin_attrib = "foo2"
 
         class TestSubStanza(ElementBase):
             name = "subfoo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         register_stanza_plugin(TestStanza, TestStanzaPlugin, iterable=True)
 
@@ -90,24 +90,24 @@ class TestElementBase(SlixTest):
         class TestStanzaPlugin(ElementBase):
             name = "pluginfoo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
             plugin_attrib = "plugin_foo"
 
         class TestStanzaPlugin2(ElementBase):
             name = "pluginfoo2"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
             plugin_attrib = "plugin_foo2"
 
         class TestSubStanza(ElementBase):
             name = "subfoo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         register_stanza_plugin(TestStanza, TestSubStanza, iterable=True)
         register_stanza_plugin(TestStanza, TestStanzaPlugin)
@@ -139,7 +139,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz', 'qux'))
+            interfaces = {'bar', 'baz', 'qux'}
             sub_interfaces = {'baz'}
 
             def get_qux(self):
@@ -185,7 +185,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz', 'qux'))
+            interfaces = {'bar', 'baz', 'qux'}
             sub_interfaces = {'baz'}
 
             def set_qux(self, value):
@@ -219,7 +219,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz', 'qux'))
+            interfaces = {'bar', 'baz', 'qux'}
             sub_interfaces = {'bar'}
 
             def del_qux(self):
@@ -261,7 +261,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         stanza = TestStanza()
 
@@ -331,7 +331,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
             def set_baz(self, value):
                 self._set_sub_text("wrapper/baz", text=value)
@@ -382,7 +382,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
             def set_bar(self, value):
                 self._set_sub_text("path/to/only/bar", value)
@@ -463,7 +463,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar','baz', 'qux'))
+            interfaces = {'bar','baz', 'qux'}
             sub_interfaces = {'qux'}
 
             def set_qux(self, value):
@@ -528,7 +528,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         stanza1 = TestStanza()
         stanza1['bar'] = 'a'
@@ -554,7 +554,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
             plugin_attrib = 'qux'
 
         register_stanza_plugin(TestStanza, TestStanza)
@@ -575,7 +575,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         stanza = TestStanza()
         stanza['bar'] = 'a'
@@ -597,7 +597,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         register_stanza_plugin(TestStanza, TestSubStanza, iterable=True)
 
@@ -652,7 +652,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         stanza1 = TestStanza()
         stanza1['bar'] = 'a'
@@ -672,7 +672,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         class TestExtension(ElementBase):
             name = 'extended'
@@ -715,7 +715,7 @@ class TestElementBase(SlixTest):
         class TestStanza(ElementBase):
             name = "foo"
             namespace = "foo"
-            interfaces = set(('bar', 'baz'))
+            interfaces = {'bar', 'baz'}
 
         class TestOverride(ElementBase):
             name = 'overrider'
diff --git a/tests/test_stream_presence.py b/tests/test_stream_presence.py
index ea2337a2..27559785 100644
--- a/tests/test_stream_presence.py
+++ b/tests/test_stream_presence.py
@@ -102,7 +102,7 @@ class TestStreamPresence(SlixTest):
                     to="tester@localhost" />
         """)
 
-        expected = set(('presence_available', 'got_online'))
+        expected = {'presence_available', 'got_online'}
         self.assertEqual(events, expected,
                 "Incorrect events triggered: %s" % events)
 
@@ -151,7 +151,7 @@ class TestStreamPresence(SlixTest):
                     type="subscribe" />
         """)
 
-        expected = set(('presence_subscribe', 'changed_subscription'))
+        expected = {'presence_subscribe', 'changed_subscription'}
         self.assertEqual(events, expected,
                 "Incorrect events triggered: %s" % events)
 
@@ -185,7 +185,7 @@ class TestStreamPresence(SlixTest):
                     type="unsubscribed" />
         """)
 
-        expected = set(('presence_subscribe', 'changed_subscription'))
+        expected = {'presence_subscribe', 'changed_subscription'}
         self.assertEqual(events, expected,
                 "Incorrect events triggered: %s" % events)