单例加锁

daacheng · daacheng · commit 71d04985f68a · 2021-04-20T00:04:31.000+08:00
&#21333;&#20363;&#21152;&#38145;
diff --git a/python_basic/new&#21644;init&#26041;&#27861;.md b/python_basic/new&#21644;init&#26041;&#27861;.md
@@ -6,14 +6,78 @@
 ## \_\_new__()&#23454;&#29616;&#21333;&#20363;
 ```python
 class Singleton:
+
     def __new__(cls, *args, **kwargs):
         if not hasattr(cls, 'instance'):
             cls.instance = super().__new__(cls)
         return cls.instance
 
-
 if __name__ == '__main__':
     s1 = Singleton()
     s2 = Singleton()
-    print(s1 is s2)  # True
+    print('s1:{}'.format(id(s1)))
+    print('s2:{}'.format(id(s2)))
+    print('s1 is s2:{}'.format(s1 is s2))
+```
+```python
+s1:1891632871352
+s2:1891632871352
+s1 is s2:True
+```
+
+**&#20197;&#19978;&#30475;&#20284;&#23454;&#29616;&#20102;&#21333;&#20363;&#27169;&#24335;&#65292;&#20294;&#23454;&#38469;&#22312;&#22810;&#32447;&#31243;&#30340;&#24773;&#20917;&#19979;&#20250;&#26377;&#38382;&#39064;&#65292;&#22810;&#20010;&#32447;&#31243;&#21516;&#26102;&#21019;&#24314;&#21333;&#20363;&#23545;&#35937;&#65292;&#22914;&#26524;&#19981;&#21152;&#38145;&#30340;&#24773;&#20917;&#19979;&#26159;&#19981;&#23433;&#20840;&#30340;&#12290;**
+
+```python
+import time
+import threading
+
+class Singleton:
+
+    def __new__(cls, *args, **kwargs):
+        if not hasattr(cls, 'instance'):
+            time.sleep(0.05)
+            cls.instance = super().__new__(cls)
+        return cls.instance
+
+def func():
+    s = Singleton()
+    print('s:{}'.format(id(s)))
+
+if __name__ == '__main__':
+    for _ in range(5):
+        # &#24320;&#21551;5&#20010;&#32447;&#31243;&#21516;&#26102;&#21019;&#24314;&#23545;&#35937;
+        td = threading.Thread(target=func)
+        td.start()
+```
+```python
+s:1230297165896
+s:1230297245008
+s:1230297372152
+s:1230297270648
+s:1230297296176
+```
+
+**&#22810;&#32447;&#31243;&#20808;&#21019;&#24314;&#21333;&#20363;&#23545;&#35937;&#38656;&#35201;&#21152;&#38145;**
+
+```python
+import threading
+
+class Singleton:
+    _instance_lock = threading.Lock()
+
+    def __new__(cls, *args, **kwargs):
+        # &#21152;&#38145;
+        with cls._instance_lock:
+            if not hasattr(cls, 'instance'):
+                cls.instance = super().__new__(cls)
+        return cls.instance
+
+def func():
+    s = Singleton()
+    print('s:{}'.format(id(s)))
+
+if __name__ == '__main__':
+    for _ in range(5):
+        td = threading.Thread(target=func)
+        td.start()
 ```
