diff --git a/PgDB.py b/PgDB.py
index efbef2a..6fcc570 100644
--- a/PgDB.py
+++ b/PgDB.py
@@ -75,25 +75,25 @@ class PgDB(object):
 	# SQL helpers
 	#
 	def _quote_value(self, value):
-		if type(value) is int or type(value) is float:
+		if isinstance(value, int) or isinstance(value, float):
 			return unicode(value)
 
-		if type(value) is str:
+		if isinstance(value, str):
 			value = unicode(value)
-		elif type(value) is datetime.datetime:
+		elif isinstance(value, datetime.datetime):
 			value = unicode(self._format_datetime(value))
-		elif type(value) is datetime.date:
+		elif isinstance(value, datetime.date):
 			value = unicode(self._format_date(value))
 
 		return u"'%s'" % value.replace(u"'",u"''")
 
 	def _format_where_clauses(self, where_clauses, where_op=u'AND'):
-		if type(where_clauses) is str:
+		if isinstance(where_clauses, str):
 			return where_clauses
-		elif type(where_clauses) is list:
+		elif isinstance(where_clauses, list):
 			return (u" %s " % where_op).join(where_clauses)
-		elif type(where_clauses) is dict:
-			return (u" %s " % where_op).join(map(lambda x: "%s=%s" % (x, _quote_value(where_clauses[x])), where_clauses))
+		elif isinstance(where_clauses, dict):
+			return (u" %s " % where_op).join(map(lambda x: "%s=%s" % (x, self._quote_value(where_clauses[x])), where_clauses))
 		logging.error('Unsupported where clauses type %s', type(where_clauses))
 		return False
 
@@ -160,7 +160,7 @@ class PgDB(object):
 		sql = u"SELECT "
 		if fields is None:
 			sql += "*"
-		elif type(fields) in (str, unicode):
+		elif isinstance(fields, str) or isinstance(fields, unicode):
 			sql += fields
 		else:
 			sql += u", ".join(fields)