From 2fcfa79ffd4c59a2a7e22ee3095b66c0143e59a7 Mon Sep 17 00:00:00 2001
From: Roman Mogilatov <rmogilatov@gmail.com>
Date: Wed, 8 Jun 2016 17:02:39 +0300
Subject: [PATCH] Fix singleton bugs related to thread-safety and checks for
 sequence types

---
 dependency_injector/providers/creational.py | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/dependency_injector/providers/creational.py b/dependency_injector/providers/creational.py
index 40c72133..46f36211 100644
--- a/dependency_injector/providers/creational.py
+++ b/dependency_injector/providers/creational.py
@@ -212,12 +212,10 @@ class Singleton(Factory):
 
         :rtype: object
         """
-        if self.instance:
-            return self.instance
-
         with GLOBAL_LOCK:
-            self.instance = super(Singleton, self)._provide(*args, **kwargs)
-
+            if self.instance is None:
+                self.instance = super(Singleton, self)._provide(*args,
+                                                                **kwargs)
         return self.instance