diff --git a/electrumx_rpc.py b/electrumx_rpc.py
index 8666df6..8cffa3b 100755
--- a/electrumx_rpc.py
+++ b/electrumx_rpc.py
@@ -71,7 +71,7 @@ def rpc_send_and_wait(port, method, params, timeout=15):
 
 def main():
     '''Send the RPC command to the server and print the result.'''
-    parser = argparse.ArgumentParser('Send electrumx an RPC command' )
+    parser = argparse.ArgumentParser('Send electrumx an RPC command')
     parser.add_argument('-p', '--port', metavar='port_num', type=int,
                         help='RPC port number')
     parser.add_argument('command', nargs=1, default=[],
diff --git a/electrumx_server.py b/electrumx_server.py
index f23542f..dd57f2a 100755
--- a/electrumx_server.py
+++ b/electrumx_server.py
@@ -25,6 +25,7 @@ SUPPRESS_MESSAGES = [
     'Fatal write error on socket transport',
 ]
 
+
 def main_loop():
     '''Start the server.'''
     if os.geteuid() == 0:
@@ -32,7 +33,7 @@ def main_loop():
                         'account and use that')
 
     loop = asyncio.get_event_loop()
-    #loop.set_debug(True)
+    # loop.set_debug(True)
 
     def on_signal(signame):
         '''Call on receipt of a signal to cleanly shutdown.'''
@@ -43,7 +44,7 @@ def main_loop():
     def on_exception(loop, context):
         '''Suppress spurious messages it appears we cannot control.'''
         message = context.get('message')
-        if not message in SUPPRESS_MESSAGES:
+        if message not in SUPPRESS_MESSAGES:
             if not ('task' in context and
                     'accept_connection2()' in repr(context.get('task'))):
                 loop.default_exception_handler(context)
diff --git a/lib/coins.py b/lib/coins.py
index aaac853..fb5391d 100644
--- a/lib/coins.py
+++ b/lib/coins.py
@@ -498,7 +498,7 @@ class DashTestnet(Dash):
     TX_PER_BLOCK = 1
     RPC_PORT = 19998
     IRC_PREFIX = "d_"
-    PEER_DEFAULT_PORTS = {'t':'51001', 's':'51002'}
+    PEER_DEFAULT_PORTS = {'t': '51001', 's': '51002'}
     PEERS = [
         'electrum.dash.siampm.com s t',
     ]
diff --git a/lib/tx.py b/lib/tx.py
index 41e4583..6fa24ad 100644
--- a/lib/tx.py
+++ b/lib/tx.py
@@ -43,6 +43,7 @@ class Tx(namedtuple("Tx", "version inputs outputs locktime")):
 
     # FIXME: add hash as a cached property?
 
+
 class TxInput(namedtuple("TxInput", "prev_hash prev_idx script sequence")):
     '''Class representing a transaction input.'''
 
@@ -117,10 +118,10 @@ class Deserializer(object):
 
     def _read_input(self):
         return TxInput(
-            self._read_nbytes(32),  # prev_hash
-            self._read_le_uint32(), # prev_idx
-            self._read_varbytes(),  # script
-            self._read_le_uint32()  # sequence
+            self._read_nbytes(32),   # prev_hash
+            self._read_le_uint32(),  # prev_idx
+            self._read_varbytes(),   # script
+            self._read_le_uint32()   # sequence
         )
 
     def _read_outputs(self):
diff --git a/lib/util.py b/lib/util.py
index fdd6dfe..991c68c 100644
--- a/lib/util.py
+++ b/lib/util.py
@@ -127,6 +127,7 @@ def deep_getsizeof(obj):
 
     return size(obj)
 
+
 def subclasses(base_class, strict=True):
     '''Return a list of subclasses of base_class in its module.'''
     def select(obj):
diff --git a/query.py b/query.py
index 283f33d..995ce7b 100755
--- a/query.py
+++ b/query.py
@@ -71,5 +71,6 @@ def main():
         print('Balance: {} {}'.format(coin.decimal_value(balance),
                                       coin.SHORTNAME))
 
+
 if __name__ == '__main__':
     main()
diff --git a/server/block_processor.py b/server/block_processor.py
index c8bdd22..e449c37 100644
--- a/server/block_processor.py
+++ b/server/block_processor.py
@@ -735,7 +735,7 @@ class BlockProcessor(server.db.DB):
         for cache_key, cache_value in self.utxo_cache.items():
             # suffix = tx_idx + tx_num
             hashX = cache_value[:-12]
-            suffix =  cache_key[-2:] + cache_value[-12:-8]
+            suffix = cache_key[-2:] + cache_value[-12:-8]
             batch_put(b'h' + cache_key[:4] + suffix, hashX)
             batch_put(b'u' + hashX + suffix, cache_value[-8:])
         self.utxo_cache = {}
diff --git a/server/controller.py b/server/controller.py
index 52694b2..07b21ac 100644
--- a/server/controller.py
+++ b/server/controller.py
@@ -167,7 +167,7 @@ class Controller(util.LoggedClass):
 
     def enqueue_session(self, session):
         # Might have disconnected whilst waiting
-        if not session in self.sessions:
+        if session not in self.sessions:
             return
         priority = self.session_priority(session)
         item = (priority, self.next_queue_id, session)
@@ -283,7 +283,7 @@ class Controller(util.LoggedClass):
             future.cancel()
 
         # Wait for all futures to finish
-        while not all (future.done() for future in self.futures):
+        while not all(future.done() for future in self.futures):
             await asyncio.sleep(0.1)
 
         # Finally shut down the block processor and executor
@@ -336,7 +336,7 @@ class Controller(util.LoggedClass):
         '''
         self.state = self.LISTENING
 
-        env= self.env
+        env = self.env
         if env.tcp_port is not None:
             await self.start_server('TCP', env.host, env.tcp_port)
         if env.ssl_port is not None:
diff --git a/server/mempool.py b/server/mempool.py
index 387b12c..d957905 100644
--- a/server/mempool.py
+++ b/server/mempool.py
@@ -93,8 +93,8 @@ class MemPool(util.LoggedClass):
         process_some = self.async_process_some(unfetched, fetch_size // 2)
 
         await self.daemon.mempool_refresh_event.wait()
-        self.logger.info ('beginning processing of daemon mempool.  '
-                          'This can take some time...')
+        self.logger.info('beginning processing of daemon mempool.  '
+                         'This can take some time...')
         next_log = 0
         loops = -1  # Zero during initial catchup
 
@@ -187,7 +187,7 @@ class MemPool(util.LoggedClass):
 
         # Skip hashes the daemon has dropped.  Either they were
         # evicted or they got in a block.
-        return {hh:raw for hh, raw in zip(hex_hashes, raw_txs) if raw}
+        return {hh: raw for hh, raw in zip(hex_hashes, raw_txs) if raw}
 
     def process_raw_txs(self, raw_tx_map, pending):
         '''Process the dictionary of raw transactions and return a dictionary
@@ -204,7 +204,7 @@ class MemPool(util.LoggedClass):
 
         # Deserialize each tx and put it in our priority queue
         for tx_hash, raw_tx in raw_tx_map.items():
-            if not tx_hash in txs:
+            if tx_hash not in txs:
                 continue
             tx, _tx_hash = deserializer(raw_tx).read_tx()
 
@@ -267,7 +267,7 @@ class MemPool(util.LoggedClass):
         unconfirmed is True if any txin is unconfirmed.
         '''
         # hashXs is a defaultdict
-        if not hashX in self.hashXs:
+        if hashX not in self.hashXs:
             return []
 
         deserializer = self.coin.deserializer()
diff --git a/server/storage.py b/server/storage.py
index 074d8a3..6562d33 100644
--- a/server/storage.py
+++ b/server/storage.py
@@ -12,6 +12,7 @@ from functools import partial
 
 import lib.util as util
 
+
 def db_class(name):
     '''Returns a DB engine class.'''
     for db_class in util.subclasses(Storage):
diff --git a/tests/test_storage.py b/tests/test_storage.py
index 910019e..afad2e1 100644
--- a/tests/test_storage.py
+++ b/tests/test_storage.py
@@ -44,8 +44,8 @@ def test_batch(db):
 
 def test_iterator(db):
     """
-    The iterator should contain all key/value pairs starting with prefix ordered
-    by key.
+    The iterator should contain all key/value pairs starting with prefix
+    ordered by key.
     """
     for i in range(5):
         db.put(b"abc" + str.encode(str(i)), str.encode(str(i)))
diff --git a/tests/test_util.py b/tests/test_util.py
index bb98c83..4142679 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -19,7 +19,6 @@ def test_cachedproperty():
             cls.CALL_COUNT += 1
             return cls.CALL_COUNT
 
-
     t = Target()
     assert t.prop == t.prop == 1
     assert Target.cls_prop == Target.cls_prop == 1
@@ -56,4 +55,4 @@ def test_chunks():
 def test_increment_byte_string():
     assert util.increment_byte_string(b'1') == b'2'
     assert util.increment_byte_string(b'\x01\x01') == b'\x01\x02'
-    assert util.increment_byte_string(b'\xff\xff') == None
+    assert util.increment_byte_string(b'\xff\xff') is None