Add some example

Author: phyng

8.25.py

@@ -0,0 +1,25 @@
+# coding: utf-8
+
+from __future__ import print_function
+import weakref
+
+class Spam:
+
+    def __init__(self, name):
+        self.name = name
+
+    def __str__(self):
+        return self.name
+
+_span_cache = weakref.WeakValueDictionary()
+def get_spam(name):
+    if name in _span_cache:
+        return _span_cache[name]
+    else:
+        spam = Spam(name)
+        _span_cache[name] = spam
+        return spam
+
+a = get_spam('foo')
+b = get_spam('bar')
+print(_span_cache.items())

9.1.py

@@ -0,0 +1,24 @@
+# coding: utf-8
+
+from __future__ import print_function
+import time
+from functools import wraps
+
+
+def timethis(func):
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        start = time.time()
+        result = func(*args, **kwargs)
+        end = time.time()
+        print(end - start)
+    return wrapper
+
+@timethis
+def test():
+    time.sleep(1)
+
+print(test.__name__)
+print(dir(test))
+print(test.__wrapped__)
+test()

9.13.py

@@ -0,0 +1,26 @@
+# coding: utf-8
+
+
+class Singleton(type):
+    def __init__(self, *args, **kwargs):
+        self.__instance = None
+        super(Singleton, self).__init__(*args, **kwargs)
+
+    def __call__(self, *args, **kwargs):
+        if self.__instance is None:
+            self.__instance = super(Singleton, self).__call__(*args, **kwargs)
+            return self.__instance
+        else:
+            return self.__instance
+
+
+class Spam():
+    __metaclass__ = Singleton
+    def __init__(self):
+        print('Creating Spam')
+
+
+a = Spam()
+b = Spam()
+
+print a is b