Consistently use six's iteritems and wrap lazy keys/values in list() if they're not meant to be lazy (#3307)

29 files changed, 116 insertions, 101 deletions

diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index b052cf532b..06fa38366d 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -15,6 +15,8 @@
 
 import logging
 
+from six import itervalues
+
 import pymacaroons
 from twisted.internet import defer
 
@@ -66,7 +68,7 @@ class Auth(object):
         )
         auth_events = yield self.store.get_events(auth_events_ids)
         auth_events = {
-            (e.type, e.state_key): e for e in auth_events.values()
+            (e.type, e.state_key): e for e in itervalues(auth_events)
         }
         self.check(event, auth_events=auth_events, do_sig_check=do_sig_check)
 
diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index db43219d24..dbc0e7e445 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -411,7 +411,7 @@ class Filter(object):
         return room_ids
 
     def filter(self, events):
-        return filter(self.check, events)
+        return list(filter(self.check, events))
 
     def limit(self):
         return self.filter_json.get("limit", 10)
diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index cd5627e36a..eaf9cecde6 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -471,14 +471,14 @@ def _check_power_levels(event, auth_events):
     ]
 
     old_list = current_state.content.get("users", {})
-    for user in set(old_list.keys() + user_list.keys()):
+    for user in set(list(old_list) + list(user_list)):
         levels_to_check.append(
             (user, "users")
         )
 
     old_list = current_state.content.get("events", {})
     new_list = event.content.get("events", {})
-    for ev_id in set(old_list.keys() + new_list.keys()):
+    for ev_id in set(list(old_list) + list(new_list)):
         levels_to_check.append(
             (ev_id, "events")
         )
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index c3ff85c49a..cb08da4984 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -146,7 +146,7 @@ class EventBase(object):
         return field in self._event_dict
 
     def items(self):
-        return self._event_dict.items()
+        return list(self._event_dict.items())
 
 
 class FrozenEvent(EventBase):
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 2761ffae07..87a92f6ea9 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -391,7 +391,7 @@ class FederationClient(FederationBase):
         """
         if return_local:
             seen_events = yield self.store.get_events(event_ids, allow_rejected=True)
-            signed_events = seen_events.values()
+            signed_events = list(seen_events.values())
         else:
             seen_events = yield self.store.have_seen_events(event_ids)
             signed_events = []
@@ -589,7 +589,7 @@ class FederationClient(FederationBase):
                 }
 
                 valid_pdus = yield self._check_sigs_and_hash_and_fetch(
-                    destination, pdus.values(),
+                    destination, list(pdus.values()),
                     outlier=True,
                 )
 
diff --git a/synapse/federation/send_queue.py b/synapse/federation/send_queue.py
index c7ed465617..3dcc629d44 100644
--- a/synapse/federation/send_queue.py
+++ b/synapse/federation/send_queue.py
@@ -197,7 +197,7 @@ class FederationRemoteSendQueue(object):
 
         # We only want to send presence for our own users, so lets always just
         # filter here just in case.
-        local_states = filter(lambda s: self.is_mine_id(s.user_id), states)
+        local_states = list(filter(lambda s: self.is_mine_id(s.user_id), states))
 
         self.presence_map.update({state.user_id: state for state in local_states})
         self.presence_changed[pos] = [state.user_id for state in local_states]
diff --git a/synapse/federation/transaction_queue.py b/synapse/federation/transaction_queue.py
index 69312ec233..f0aeb5a0d3 100644
--- a/synapse/federation/transaction_queue.py
+++ b/synapse/federation/transaction_queue.py
@@ -35,6 +35,8 @@ from synapse.metrics import (
 
 from prometheus_client import Counter
 
+from six import itervalues
+
 import logging
 
 
@@ -234,7 +236,7 @@ class TransactionQueue(object):
                 yield logcontext.make_deferred_yieldable(defer.gatherResults(
                     [
                         logcontext.run_in_background(handle_room_events, evs)
-                        for evs in events_by_room.itervalues()
+                        for evs in itervalues(events_by_room)
                     ],
                     consumeErrors=True
                 ))
@@ -325,7 +327,7 @@ class TransactionQueue(object):
                 if not states_map:
                     break
 
-                yield self._process_presence_inner(states_map.values())
+                yield self._process_presence_inner(list(states_map.values()))
         except Exception:
             logger.exception("Error sending presence states to servers")
         finally:
diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index e089e66fde..2d1db0c245 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -114,14 +114,14 @@ class BaseHandler(object):
             if guest_access != "can_join":
                 if context:
                     current_state = yield self.store.get_events(
-                        context.current_state_ids.values()
+                        list(context.current_state_ids.values())
                     )
                 else:
                     current_state = yield self.state_handler.get_current_state(
                         event.room_id
                     )
 
-                current_state = current_state.values()
+                current_state = list(current_state.values())
 
                 logger.info("maybe_kick_guest_users %r", current_state)
                 yield self.kick_guest_users(current_state)
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index d9f35a5dba..1c29c43a83 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -15,6 +15,8 @@
 
 from twisted.internet import defer
 
+from six import itervalues
+
 import synapse
 from synapse.api.constants import EventTypes
 from synapse.util.metrics import Measure
@@ -119,7 +121,7 @@ class ApplicationServicesHandler(object):
 
                     yield make_deferred_yieldable(defer.gatherResults([
                         run_in_background(handle_room_events, evs)
-                        for evs in events_by_room.itervalues()
+                        for evs in itervalues(events_by_room)
                     ], consumeErrors=True))
 
                     yield self.store.set_appservice_last_pos(upper_bound)
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index a5365c4fe4..3c0051586d 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -249,7 +249,7 @@ class AuthHandler(BaseHandler):
                 errordict = e.error_dict()
 
         for f in flows:
-            if len(set(f) - set(creds.keys())) == 0:
+            if len(set(f) - set(creds)) == 0:
                 # it's very useful to know what args are stored, but this can
                 # include the password in the case of registering, so only log
                 # the keys (confusingly, clientdict may contain a password
@@ -257,12 +257,12 @@ class AuthHandler(BaseHandler):
                 # and is not sensitive).
                 logger.info(
                     "Auth completed with creds: %r. Client dict has keys: %r",
-                    creds, clientdict.keys()
+                    creds, list(clientdict)
                 )
                 defer.returnValue((creds, clientdict, session['id']))
 
         ret = self._auth_dict_for_flows(flows, session)
-        ret['completed'] = creds.keys()
+        ret['completed'] = list(creds)
         ret.update(errordict)
         raise InteractiveAuthIncompleteError(
             ret,
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index 31bd0e60c6..11c6fb3657 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -114,7 +114,7 @@ class DeviceHandler(BaseHandler):
             user_id, device_id=None
         )
 
-        devices = device_map.values()
+        devices = list(device_map.values())
         for device in devices:
             _update_device_from_client_ips(device, ips)
 
@@ -187,7 +187,7 @@ class DeviceHandler(BaseHandler):
             defer.Deferred:
         """
         device_map = yield self.store.get_devices_by_user(user_id)
-        device_ids = device_map.keys()
+        device_ids = list(device_map)
         if except_device_id is not None:
             device_ids = [d for d in device_ids if d != except_device_id]
         yield self.delete_devices(user_id, device_ids)
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 87c0615820..fcf94befb7 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -52,7 +52,6 @@ from synapse.util.retryutils import NotRetryingDestination
 
 from synapse.util.distributor import user_joined_room
 
-
 logger = logging.getLogger(__name__)
 
 
@@ -480,8 +479,8 @@ class FederationHandler(BaseHandler):
         # to get all state ids that we're interested in.
         event_map = yield self.store.get_events([
             e_id
-            for key_to_eid in event_to_state_ids.itervalues()
-            for key, e_id in key_to_eid.iteritems()
+            for key_to_eid in list(event_to_state_ids.values())
+            for key, e_id in key_to_eid.items()
             if key[0] != EventTypes.Member or check_match(key[1])
         ])
 
@@ -1149,13 +1148,13 @@ class FederationHandler(BaseHandler):
                 user = UserID.from_string(event.state_key)
                 yield user_joined_room(self.distributor, user, event.room_id)
 
-        state_ids = context.prev_state_ids.values()
+        state_ids = list(context.prev_state_ids.values())
         auth_chain = yield self.store.get_auth_chain(state_ids)
 
-        state = yield self.store.get_events(context.prev_state_ids.values())
+        state = yield self.store.get_events(list(context.prev_state_ids.values()))
 
         defer.returnValue({
-            "state": state.values(),
+            "state": list(state.values()),
             "auth_chain": auth_chain,
         })
 
@@ -1405,7 +1404,7 @@ class FederationHandler(BaseHandler):
                 else:
                     del results[(event.type, event.state_key)]
 
-            res = results.values()
+            res = list(results.values())
             for event in res:
                 # We sign these again because there was a bug where we
                 # incorrectly signed things the first time round
@@ -1446,7 +1445,7 @@ class FederationHandler(BaseHandler):
                 else:
                     results.pop((event.type, event.state_key), None)
 
-            defer.returnValue(results.values())
+            defer.returnValue(list(results.values()))
         else:
             defer.returnValue([])
 
@@ -1915,7 +1914,7 @@ class FederationHandler(BaseHandler):
                 })
 
                 new_state = self.state_handler.resolve_events(
-                    [local_view.values(), remote_view.values()],
+                    [list(local_view.values()), list(remote_view.values())],
                     event
                 )
 
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 26fc0d3ec7..7fe568132f 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -325,7 +325,7 @@ class PresenceHandler(object):
 
             if to_notify:
                 notified_presence_counter.inc(len(to_notify))
-                yield self._persist_and_notify(to_notify.values())
+                yield self._persist_and_notify(list(to_notify.values()))
 
             self.unpersisted_users_changes |= set(s.user_id for s in new_states)
             self.unpersisted_users_changes -= set(to_notify.keys())
@@ -687,7 +687,7 @@ class PresenceHandler(object):
         """
 
         updates = yield self.current_state_for_users(target_user_ids)
-        updates = updates.values()
+        updates = list(updates.values())
 
         for user_id in set(target_user_ids) - set(u.user_id for u in updates):
             updates.append(UserPresenceState.default(user_id))
@@ -753,11 +753,11 @@ class PresenceHandler(object):
             self._push_to_remotes([state])
         else:
             user_ids = yield self.store.get_users_in_room(room_id)
-            user_ids = filter(self.is_mine_id, user_ids)
+            user_ids = list(filter(self.is_mine_id, user_ids))
 
             states = yield self.current_state_for_users(user_ids)
 
-            self._push_to_remotes(states.values())
+            self._push_to_remotes(list(states.values()))
 
     @defer.inlineCallbacks
     def get_presence_list(self, observer_user, accepted=None):
@@ -1051,7 +1051,7 @@ class PresenceEventSource(object):
             updates = yield presence.current_state_for_users(user_ids_changed)
 
         if include_offline:
-            defer.returnValue((updates.values(), max_token))
+            defer.returnValue((list(updates.values()), max_token))
         else:
             defer.returnValue(([
                 s for s in itervalues(updates)
@@ -1112,7 +1112,7 @@ def handle_timeouts(user_states, is_mine_fn, syncing_user_ids, now):
         if new_state:
             changes[state.user_id] = new_state
 
-    return changes.values()
+    return list(changes.values())
 
 
 def handle_timeout(state, is_mine, syncing_user_ids, now):
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index b5850db42f..2abd63ad05 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -455,7 +455,7 @@ class RoomContextHandler(BaseHandler):
         state = yield self.store.get_state_for_events(
             [last_event_id], None
         )
-        results["state"] = state[last_event_id].values()
+        results["state"] = list(state[last_event_id].values())
 
         results["start"] = now_token.copy_and_replace(
             "room_key", results["start"]
diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index 5757bb7f8a..fc507cef36 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -15,6 +15,7 @@
 
 from twisted.internet import defer
 
+from six import iteritems
 from six.moves import range
 
 from ._base import BaseHandler
@@ -307,7 +308,7 @@ class RoomListHandler(BaseHandler):
         )
 
         event_map = yield self.store.get_events([
-            event_id for key, event_id in current_state_ids.iteritems()
+            event_id for key, event_id in iteritems(current_state_ids)
             if key[0] in (
                 EventTypes.JoinRules,
                 EventTypes.Name,
diff --git a/synapse/handlers/search.py b/synapse/handlers/search.py
index 9772ed1a0e..1eca26aa1e 100644
--- a/synapse/handlers/search.py
+++ b/synapse/handlers/search.py
@@ -348,7 +348,7 @@ class SearchHandler(BaseHandler):
             rooms = set(e.room_id for e in allowed_events)
             for room_id in rooms:
                 state = yield self.state_handler.get_current_state(room_id)
-                state_results[room_id] = state.values()
+                state_results[room_id] = list(state.values())
 
             state_results.values()
 
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 8377650b68..51ec727df0 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -541,11 +541,11 @@ class SyncHandler(object):
 
         state = {}
         if state_ids:
-            state = yield self.store.get_events(state_ids.values())
+            state = yield self.store.get_events(list(state_ids.values()))
 
         defer.returnValue({
             (e.type, e.state_key): e
-            for e in sync_config.filter_collection.filter_room_state(state.values())
+            for e in sync_config.filter_collection.filter_room_state(list(state.values()))
         })
 
     @defer.inlineCallbacks
@@ -894,7 +894,7 @@ class SyncHandler(object):
             presence.extend(states)
 
             # Deduplicate the presence entries so that there's at most one per user
-            presence = {p.user_id: p for p in presence}.values()
+            presence = list({p.user_id: p for p in presence}.values())
 
         presence = sync_config.filter_collection.filter_presence(
             presence
diff --git a/synapse/push/baserules.py b/synapse/push/baserules.py
index 7a18afe5f9..a8ae7bcd6c 100644
--- a/synapse/push/baserules.py
+++ b/synapse/push/baserules.py
@@ -39,7 +39,7 @@ def list_with_base_rules(rawrules):
     rawrules = [r for r in rawrules if r['priority_class'] >= 0]
 
     # shove the server default rules for each kind onto the end of each
-    current_prio_class = PRIORITY_CLASS_INVERSE_MAP.keys()[-1]
+    current_prio_class = list(PRIORITY_CLASS_INVERSE_MAP)[-1]
 
     ruleslist.extend(make_base_prepend_rules(
         PRIORITY_CLASS_INVERSE_MAP[current_prio_class], modified_base_rules
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index b5cd9b426a..d4be800e5e 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -229,7 +229,8 @@ class Mailer(object):
                 if room_vars['notifs'] and 'messages' in room_vars['notifs'][-1]:
                     prev_messages = room_vars['notifs'][-1]['messages']
                     for message in notifvars['messages']:
-                        pm = filter(lambda pm: pm['id'] == message['id'], prev_messages)
+                        pm = list(filter(lambda pm: pm['id'] == message['id'],
+                                         prev_messages))
                         if pm:
                             if not message["is_historical"]:
                                 pm[0]["is_historical"] = False
diff --git a/synapse/push/presentable_names.py b/synapse/push/presentable_names.py
index 277da3cd35..43f0c74ff3 100644
--- a/synapse/push/presentable_names.py
+++ b/synapse/push/presentable_names.py
@@ -113,7 +113,7 @@ def calculate_room_name(store, room_state_ids, user_id, fallback_to_members=True
     # so find out who is in the room that isn't the user.
     if "m.room.member" in room_state_bytype_ids:
         member_events = yield store.get_events(
-            room_state_bytype_ids["m.room.member"].values()
+            list(room_state_bytype_ids["m.room.member"].values())
         )
         all_members = [
             ev for ev in member_events.values()
diff --git a/synapse/rest/client/transactions.py b/synapse/rest/client/transactions.py
index 20fa6678ef..7c01b438cb 100644
--- a/synapse/rest/client/transactions.py
+++ b/synapse/rest/client/transactions.py
@@ -104,7 +104,7 @@ class HttpTransactionCache(object):
 
     def _cleanup(self):
         now = self.clock.time_msec()
-        for key in self.transactions.keys():
+        for key in list(self.transactions):
             ts = self.transactions[key][1]
             if now > (ts + CLEANUP_PERIOD_MS):  # after cleanup period
                 del self.transactions[key]
diff --git a/synapse/state.py b/synapse/state.py
index b8c27c6815..216418f58d 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -132,7 +132,8 @@ class StateHandler(object):
             defer.returnValue(event)
             return
 
-        state_map = yield self.store.get_events(state.values(), get_prev_content=False)
+        state_map = yield self.store.get_events(list(state.values()),
+                                                get_prev_content=False)
         state = {
             key: state_map[e_id] for key, e_id in iteritems(state) if e_id in state_map
         }
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index b96104ccae..cb1082e864 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -40,6 +40,9 @@ import synapse.metrics
 from synapse.events import EventBase    # noqa: F401
 from synapse.events.snapshot import EventContext   # noqa: F401
 
+from six.moves import range
+from six import itervalues, iteritems
+
 from prometheus_client import Counter
 
 logger = logging.getLogger(__name__)
@@ -245,7 +248,7 @@ class EventsStore(EventsWorkerStore):
             partitioned.setdefault(event.room_id, []).append((event, ctx))
 
         deferreds = []
-        for room_id, evs_ctxs in partitioned.iteritems():
+        for room_id, evs_ctxs in iteritems(partitioned):
             d = self._event_persist_queue.add_to_queue(
                 room_id, evs_ctxs,
                 backfilled=backfilled,
@@ -330,7 +333,7 @@ class EventsStore(EventsWorkerStore):
 
             chunks = [
                 events_and_contexts[x:x + 100]
-                for x in xrange(0, len(events_and_contexts), 100)
+                for x in range(0, len(events_and_contexts), 100)
             ]
 
             for chunk in chunks:
@@ -364,7 +367,7 @@ class EventsStore(EventsWorkerStore):
                                 (event, context)
                             )
 
-                        for room_id, ev_ctx_rm in events_by_room.iteritems():
+                        for room_id, ev_ctx_rm in iteritems(events_by_room):
                             # Work out new extremities by recursively adding and removing
                             # the new events.
                             latest_event_ids = yield self.get_latest_event_ids_in_room(
@@ -459,12 +462,12 @@ class EventsStore(EventsWorkerStore):
 
                     event_counter.labels(event.type, origin_type, origin_entity).inc()
 
-                for room_id, new_state in current_state_for_room.iteritems():
+                for room_id, new_state in iteritems(current_state_for_room):
                     self.get_current_state_ids.prefill(
                         (room_id, ), new_state
                     )
 
-                for room_id, latest_event_ids in new_forward_extremeties.iteritems():
+                for room_id, latest_event_ids in iteritems(new_forward_extremeties):
                     self.get_latest_event_ids_in_room.prefill(
                         (room_id,), list(latest_event_ids)
                     )
@@ -641,20 +644,20 @@ class EventsStore(EventsWorkerStore):
         """
         existing_state = yield self.get_current_state_ids(room_id)
 
-        existing_events = set(existing_state.itervalues())
-        new_events = set(ev_id for ev_id in current_state.itervalues())
+        existing_events = set(itervalues(existing_state))
+        new_events = set(ev_id for ev_id in itervalues(current_state))
         changed_events = existing_events ^ new_events
 
         if not changed_events:
             return
 
         to_delete = {
-            key: ev_id for key, ev_id in existing_state.iteritems()
+            key: ev_id for key, ev_id in iteritems(existing_state)
             if ev_id in changed_events
         }
         events_to_insert = (new_events - existing_events)
         to_insert = {
-            key: ev_id for key, ev_id in current_state.iteritems()
+            key: ev_id for key, ev_id in iteritems(current_state)
             if ev_id in events_to_insert
         }
 
@@ -757,11 +760,11 @@ class EventsStore(EventsWorkerStore):
         )
 
     def _update_current_state_txn(self, txn, state_delta_by_room, max_stream_order):
-        for room_id, current_state_tuple in state_delta_by_room.iteritems():
+        for room_id, current_state_tuple in iteritems(state_delta_by_room):
                 to_delete, to_insert = current_state_tuple
                 txn.executemany(
                     "DELETE FROM current_state_events WHERE event_id = ?",
-                    [(ev_id,) for ev_id in to_delete.itervalues()],
+                    [(ev_id,) for ev_id in itervalues(to_delete)],
                 )
 
                 self._simple_insert_many_txn(
@@ -774,7 +777,7 @@ class EventsStore(EventsWorkerStore):
                             "type": key[0],
                             "state_key": key[1],
                         }
-                        for key, ev_id in to_insert.iteritems()
+                        for key, ev_id in iteritems(to_insert)
                     ],
                 )
 
@@ -793,7 +796,7 @@ class EventsStore(EventsWorkerStore):
                             "event_id": ev_id,
                             "prev_event_id": to_delete.get(key, None),
                         }
-                        for key, ev_id in state_deltas.iteritems()
+                        for key, ev_id in iteritems(state_deltas)
                     ]
                 )
 
@@ -836,7 +839,7 @@ class EventsStore(EventsWorkerStore):
 
     def _update_forward_extremities_txn(self, txn, new_forward_extremities,
                                         max_stream_order):
-        for room_id, new_extrem in new_forward_extremities.iteritems():
+        for room_id, new_extrem in iteritems(new_forward_extremities):
             self._simple_delete_txn(
                 txn,
                 table="event_forward_extremities",
@@ -854,7 +857,7 @@ class EventsStore(EventsWorkerStore):
                     "event_id": ev_id,
                     "room_id": room_id,
                 }
-                for room_id, new_extrem in new_forward_extremities.iteritems()
+                for room_id, new_extrem in iteritems(new_forward_extremities)
                 for ev_id in new_extrem
             ],
         )
@@ -871,7 +874,7 @@ class EventsStore(EventsWorkerStore):
                     "event_id": event_id,
                     "stream_ordering": max_stream_order,
                 }
-                for room_id, new_extrem in new_forward_extremities.iteritems()
+                for room_id, new_extrem in iteritems(new_forward_extremities)
                 for event_id in new_extrem
             ]
         )
@@ -899,7 +902,7 @@ class EventsStore(EventsWorkerStore):
                         new_events_and_contexts[event.event_id] = (event, context)
             else:
                 new_events_and_contexts[event.event_id] = (event, context)
-        return new_events_and_contexts.values()
+        return list(new_events_and_contexts.values())
 
     def _update_room_depths_txn(self, txn, events_and_contexts, backfilled):
         """Update min_depth for each room
@@ -925,7 +928,7 @@ class EventsStore(EventsWorkerStore):
                     event.depth, depth_updates.get(event.room_id, event.depth)
                 )
 
-        for room_id, depth in depth_updates.iteritems():
+        for room_id, depth in iteritems(depth_updates):
             self._update_min_depth_for_room_txn(txn, room_id, depth)
 
     def _update_outliers_txn(self, txn, events_and_contexts):
@@ -1309,7 +1312,7 @@ class EventsStore(EventsWorkerStore):
                 " WHERE e.event_id IN (%s)"
             ) % (",".join(["?"] * len(ev_map)),)
 
-            txn.execute(sql, ev_map.keys())
+            txn.execute(sql, list(ev_map))
             rows = self.cursor_to_dict(txn)
             for row in rows:
                 event = ev_map[row["event_id"]]
@@ -1572,7 +1575,7 @@ class EventsStore(EventsWorkerStore):
 
             chunks = [
                 event_ids[i:i + 100]
-                for i in xrange(0, len(event_ids), 100)
+                for i in range(0, len(event_ids), 100)
             ]
             for chunk in chunks:
                 ev_rows = self._simple_select_many_txn(
@@ -1986,7 +1989,7 @@ class EventsStore(EventsWorkerStore):
         logger.info("[purge] finding state groups which depend on redundant"
                     " state groups")
         remaining_state_groups = []
-        for i in xrange(0, len(state_rows), 100):
+        for i in range(0, len(state_rows), 100):
             chunk = [sg for sg, in state_rows[i:i + 100]]
             # look for state groups whose prev_state_group is one we are about
             # to delete
@@ -2042,7 +2045,7 @@ class EventsStore(EventsWorkerStore):
                         "state_key": key[1],
                         "event_id": state_id,
                     }
-                    for key, state_id in curr_state.iteritems()
+                    for key, state_id in iteritems(curr_state)
                 ],
             )
 
diff --git a/synapse/storage/presence.py b/synapse/storage/presence.py
index 9e9d3c2591..f05d91cc58 100644
--- a/synapse/storage/presence.py
+++ b/synapse/storage/presence.py
@@ -16,6 +16,7 @@
 from ._base import SQLBaseStore
 from synapse.api.constants import PresenceState
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks, cachedList
+from synapse.util import batch_iter
 
 from collections import namedtuple
 from twisted.internet import defer
@@ -115,11 +116,7 @@ class PresenceStore(SQLBaseStore):
             " AND user_id IN (%s)"
         )
 
-        batches = (
-            presence_states[i:i + 50]
-            for i in xrange(0, len(presence_states), 50)
-        )
-        for states in batches:
+        for states in batch_iter(presence_states, 50):
             args = [stream_id]
             args.extend(s.user_id for s in states)
             txn.execute(
diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index a9c299a861..f0fa5d7631 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -448,7 +448,7 @@ class SearchStore(BackgroundUpdateStore):
             "search_msgs", self.cursor_to_dict, sql, *args
         )
 
-        results = filter(lambda row: row["room_id"] in room_ids, results)
+        results = list(filter(lambda row: row["room_id"] in room_ids, results))
 
         events = yield self._get_events([r["event_id"] for r in results])
 
@@ -603,7 +603,7 @@ class SearchStore(BackgroundUpdateStore):
             "search_rooms", self.cursor_to_dict, sql, *args
         )
 
-        results = filter(lambda row: row["room_id"] in room_ids, results)
+        results = list(filter(lambda row: row["room_id"] in room_ids, results))
 
         events = yield self._get_events([r["event_id"] for r in results])
 
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index ffa4246031..bdee14a8eb 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -16,6 +16,9 @@
 from collections import namedtuple
 import logging
 
+from six import iteritems, itervalues
+from six.moves import range
+
 from twisted.internet import defer
 
 from synapse.storage.background_updates import BackgroundUpdateStore
@@ -134,7 +137,7 @@ class StateGroupWorkerStore(SQLBaseStore):
             event_ids,
         )
 
-        groups = set(event_to_groups.itervalues())
+        groups = set(itervalues(event_to_groups))
         group_to_state = yield self._get_state_for_groups(groups)
 
         defer.returnValue(group_to_state)
@@ -166,18 +169,18 @@ class StateGroupWorkerStore(SQLBaseStore):
 
         state_event_map = yield self.get_events(
             [
-                ev_id for group_ids in group_to_ids.itervalues()
-                for ev_id in group_ids.itervalues()
+                ev_id for group_ids in itervalues(group_to_ids)
+                for ev_id in itervalues(group_ids)
             ],
             get_prev_content=False
         )
 
         defer.returnValue({
             group: [
-                state_event_map[v] for v in event_id_map.itervalues()
+                state_event_map[v] for v in itervalues(event_id_map)
                 if v in state_event_map
             ]
-            for group, event_id_map in group_to_ids.iteritems()
+            for group, event_id_map in iteritems(group_to_ids)
         })
 
     @defer.inlineCallbacks
@@ -186,7 +189,7 @@ class StateGroupWorkerStore(SQLBaseStore):
         """
         results = {}
 
-        chunks = [groups[i:i + 100] for i in xrange(0, len(groups), 100)]
+        chunks = [groups[i:i + 100] for i in range(0, len(groups), 100)]
         for chunk in chunks:
             res = yield self.runInteraction(
                 "_get_state_groups_from_groups",
@@ -347,21 +350,21 @@ class StateGroupWorkerStore(SQLBaseStore):
             event_ids,
         )
 
-        groups = set(event_to_groups.itervalues())
+        groups = set(itervalues(event_to_groups))
         group_to_state = yield self._get_state_for_groups(groups, types)
 
         state_event_map = yield self.get_events(
-            [ev_id for sd in group_to_state.itervalues() for ev_id in sd.itervalues()],
+            [ev_id for sd in itervalues(group_to_state) for ev_id in itervalues(sd)],
             get_prev_content=False
         )
 
         event_to_state = {
             event_id: {
                 k: state_event_map[v]
-                for k, v in group_to_state[group].iteritems()
+                for k, v in iteritems(group_to_state[group])
                 if v in state_event_map
             }
-            for event_id, group in event_to_groups.iteritems()
+            for event_id, group in iteritems(event_to_groups)
         }
 
         defer.returnValue({event: event_to_state[event] for event in event_ids})
@@ -384,12 +387,12 @@ class StateGroupWorkerStore(SQLBaseStore):
             event_ids,
         )
 
-        groups = set(event_to_groups.itervalues())
+        groups = set(itervalues(event_to_groups))
         group_to_state = yield self._get_state_for_groups(groups, types)
 
         event_to_state = {
             event_id: group_to_state[group]
-            for event_id, group in event_to_groups.iteritems()
+            for event_id, group in iteritems(event_to_groups)
         }
 
         defer.returnValue({event: event_to_state[event] for event in event_ids})
@@ -503,7 +506,7 @@ class StateGroupWorkerStore(SQLBaseStore):
         got_all = is_all or not missing_types
 
         return {
-            k: v for k, v in state_dict_ids.iteritems()
+            k: v for k, v in iteritems(state_dict_ids)
             if include(k[0], k[1])
         }, missing_types, got_all
 
@@ -562,12 +565,12 @@ class StateGroupWorkerStore(SQLBaseStore):
 
             # Now we want to update the cache with all the things we fetched
             # from the database.
-            for group, group_state_dict in group_to_state_dict.iteritems():
+            for group, group_state_dict in iteritems(group_to_state_dict):
                 state_dict = results[group]
 
                 state_dict.update(
                     ((intern_string(k[0]), intern_string(k[1])), to_ascii(v))
-                    for k, v in group_state_dict.iteritems()
+                    for k, v in iteritems(group_state_dict)
                 )
 
                 self._state_group_cache.update(
@@ -654,7 +657,7 @@ class StateGroupWorkerStore(SQLBaseStore):
                             "state_key": key[1],
                             "event_id": state_id,
                         }
-                        for key, state_id in delta_ids.iteritems()
+                        for key, state_id in iteritems(delta_ids)
                     ],
                 )
             else:
@@ -669,7 +672,7 @@ class StateGroupWorkerStore(SQLBaseStore):
                             "state_key": key[1],
                             "event_id": state_id,
                         }
-                        for key, state_id in current_state_ids.iteritems()
+                        for key, state_id in iteritems(current_state_ids)
                     ],
                 )
 
@@ -794,11 +797,11 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
                     "state_group": state_group_id,
                     "event_id": event_id,
                 }
-                for event_id, state_group_id in state_groups.iteritems()
+                for event_id, state_group_id in iteritems(state_groups)
             ],
         )
 
-        for event_id, state_group_id in state_groups.iteritems():
+        for event_id, state_group_id in iteritems(state_groups):
             txn.call_after(
                 self._get_state_group_for_event.prefill,
                 (event_id,), state_group_id
@@ -826,7 +829,7 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
 
         def reindex_txn(txn):
             new_last_state_group = last_state_group
-            for count in xrange(batch_size):
+            for count in range(batch_size):
                 txn.execute(
                     "SELECT id, room_id FROM state_groups"
                     " WHERE ? < id AND id <= ?"
@@ -884,7 +887,7 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
                         # of keys
 
                         delta_state = {
-                            key: value for key, value in curr_state.iteritems()
+                            key: value for key, value in iteritems(curr_state)
                             if prev_state.get(key, None) != value
                         }
 
@@ -924,7 +927,7 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
                                     "state_key": key[1],
                                     "event_id": state_id,
                                 }
-                                for key, state_id in delta_state.iteritems()
+                                for key, state_id in iteritems(delta_state)
                             ],
                         )
 
diff --git a/synapse/storage/user_directory.py b/synapse/storage/user_directory.py
index d6e289ffbe..275c299998 100644
--- a/synapse/storage/user_directory.py
+++ b/synapse/storage/user_directory.py
@@ -22,6 +22,8 @@ from synapse.api.constants import EventTypes, JoinRules
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 from synapse.types import get_domain_from_id, get_localpart_from_id
 
+from six import iteritems
+
 import re
 import logging
 
@@ -100,7 +102,7 @@ class UserDirectoryStore(SQLBaseStore):
                     user_id, get_localpart_from_id(user_id), get_domain_from_id(user_id),
                     profile.display_name,
                 )
-                for user_id, profile in users_with_profile.iteritems()
+                for user_id, profile in iteritems(users_with_profile)
             )
         elif isinstance(self.database_engine, Sqlite3Engine):
             sql = """
@@ -112,7 +114,7 @@ class UserDirectoryStore(SQLBaseStore):
                     user_id,
                     "%s %s" % (user_id, p.display_name,) if p.display_name else user_id
                 )
-                for user_id, p in users_with_profile.iteritems()
+                for user_id, p in iteritems(users_with_profile)
             )
         else:
             # This should be unreachable.
@@ -130,7 +132,7 @@ class UserDirectoryStore(SQLBaseStore):
                         "display_name": profile.display_name,
                         "avatar_url": profile.avatar_url,
                     }
-                    for user_id, profile in users_with_profile.iteritems()
+                    for user_id, profile in iteritems(users_with_profile)
                 ]
             )
             for user_id in users_with_profile:
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index f4e2c30088..fc1874b65b 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -569,7 +569,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                     return results
 
                 return logcontext.make_deferred_yieldable(defer.gatherResults(
-                    cached_defers.values(),
+                    list(cached_defers.values()),
                     consumeErrors=True,
                 ).addCallback(update_results_dict).addErrback(
                     unwrapFirstError
diff --git a/synapse/util/caches/treecache.py b/synapse/util/caches/treecache.py
index fcc341a6b7..dd4c9e6067 100644
--- a/synapse/util/caches/treecache.py
+++ b/synapse/util/caches/treecache.py
@@ -1,3 +1,5 @@
+from six import itervalues
+
 SENTINEL = object()
 
 
@@ -49,7 +51,7 @@ class TreeCache(object):
         if popped is SENTINEL:
             return default
 
-        node_and_keys = zip(nodes, key)
+        node_and_keys = list(zip(nodes, key))
         node_and_keys.reverse()
         node_and_keys.append((self.root, None))
 
@@ -76,7 +78,7 @@ def iterate_tree_cache_entry(d):
     can contain dicts.
     """
     if isinstance(d, dict):
-        for value_d in d.itervalues():
+        for value_d in itervalues(d):
             for value in iterate_tree_cache_entry(value_d):
                 yield value
     else: