implemented Py2 & Py3 compatible Singleton

nhentai/downloader.py

@@ -6,14 +6,10 @@ from urlparse import urlparse
 from logger import logger
 from parser import request
 
+from nhentai.utils import Singleton
 
-class Downloader(object):
-    _instance = None
 
-    def __new__(cls, *args, **kwargs):
-        if not cls._instance:
-            cls._instance = super(Downloader, cls).__new__(cls, *args, **kwargs)
-        return cls._instance
+class Downloader(Singleton):
 
     def __init__(self, path='', thread=1, timeout=30):
         if not isinstance(thread, (int, )) or thread < 1 or thread > 10:

nhentai/utils.py

@@ -0,0 +1,10 @@
+# coding: utf-8
+class _Singleton(type):
+    """ A metaclass that creates a Singleton base class when called. """
+    _instances = {}
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(_Singleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]
+
+class Singleton(_Singleton('SingletonMeta', (object,), {})): pass