diff --git a/platypush/plugins/db/__init__.py b/platypush/plugins/db/__init__.py
index e92c2fe7e..74b76eed6 100644
--- a/platypush/plugins/db/__init__.py
+++ b/platypush/plugins/db/__init__.py
@@ -45,7 +45,7 @@ class DbPlugin(Plugin):
     _db_error_wait_interval = 5.0
     _db_error_retries = 3
 
-    def __init__(self, engine=None, *args, **kwargs):
+    def __init__(self, *args, engine=None, **kwargs):
         """
         :param engine: Default SQLAlchemy connection engine string (e.g.
             ``sqlite:///:memory:`` or ``mysql://user:pass@localhost/test``)
@@ -86,16 +86,14 @@ class DbPlugin(Plugin):
         return self.engine
 
     @staticmethod
-    def _build_condition(table, column, value):  # type: ignore
-        if isinstance(value, str):
-            value = "'{}'".format(value)
-        elif not isinstance(value, int) and not isinstance(value, float):
-            value = "'{}'".format(str(value))
+    def _build_condition(table, column, value):  # pylint: disable=unused-argument
+        if isinstance(value, str) or not isinstance(value, (int, float)):
+            value = f"'{value}'"
 
-        return eval('table.c.{}=={}'.format(column, value))
+        return eval(f'table.c.{column}=={value}')  # pylint: disable=eval-used
 
     @action
-    def execute(self, statement, engine=None, *args, **kwargs):
+    def execute(self, statement, *args, engine=None, **kwargs):
         """
         Executes a raw SQL statement.
 
@@ -123,32 +121,34 @@ class DbPlugin(Plugin):
         with engine.connect() as connection:
             connection.execute(text(statement))
 
-    def _get_table(self, table, engine=None, *args, **kwargs):
+    def _get_table(self, table: str, engine=None, *args, **kwargs):
         if not engine:
             engine = self.get_engine(engine, *args, **kwargs)
 
         db_ok = False
         n_tries = 0
         last_error = None
+        table_ = None
 
         while not db_ok and n_tries < self._db_error_retries:
             try:
                 n_tries += 1
                 metadata = MetaData()
-                table = Table(table, metadata, autoload_with=engine)
+                table_ = Table(table, metadata, autoload_with=engine)
                 db_ok = True
             except Exception as e:
                 last_error = e
                 wait_time = self._db_error_wait_interval * n_tries
                 self.logger.exception(e)
-                self.logger.info('Waiting {} seconds before retrying'.format(wait_time))
+                self.logger.info('Waiting %s seconds before retrying', wait_time)
                 time.sleep(wait_time)
                 engine = self.get_engine(engine, *args, **kwargs)
 
         if not db_ok and last_error:
             raise last_error
 
-        return table, engine
+        assert table_, f'No such table: {table}'
+        return table_, engine
 
     @action
     def select(
@@ -385,8 +385,9 @@ class DbPlugin(Plugin):
 
         query = table.select().where(
             or_(
-                and_(
-                    self._build_condition(table, k, record.get(k)) for k in key_columns
+                and_(  # type: ignore
+                    self._build_condition(table, k, record.get(k))
+                    for k in key_columns  # type: ignore
                 )
                 for record in records
             )
@@ -520,11 +521,11 @@ class DbPlugin(Plugin):
 
         with engine.connect() as connection, conn_begin(connection):
             for record in records:
-                table, engine = self._get_table(table, engine=engine, *args, **kwargs)
-                delete = table.delete()
+                table_, engine = self._get_table(table, engine=engine, *args, **kwargs)
+                delete = table_.delete()
 
                 for k, v in record.items():
-                    delete = delete.where(self._build_condition(table, k, v))
+                    delete = delete.where(self._build_condition(table_, k, v))
 
                 connection.execute(delete)