9.10小节完成~

Author: yidao620c

cookbook/c09/p09_class_decorator.py

@@ -17,11 +17,11 @@ def __call__(self, *args, **kwargs):
         self.ncalls += 1
         return self.__wrapped__(*args, **kwargs)
 
-    # def __get__(self, instance, cls):
-    #     if instance is None:
-    #         return self
-    #     else:
-    #         return types.MethodType(self, instance)
+    def __get__(self, instance, cls):
+        if instance is None:
+            return self
+        else:
+            return types.MethodType(self, instance)
 
 @Profiled
 def add(x, y):

cookbook/c09/p10_static_decorator.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+# -*- encoding: utf-8 -*-
+"""
+Topic: sample
+Desc : 
+"""
+
+import time
+from functools import wraps
+
+# A simple decorator
+def timethis(func):
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        start = time.time()
+        r = func(*args, **kwargs)
+        end = time.time()
+        print(end-start)
+        return r
+    return wrapper
+
+# Class illustrating application of the decorator to different kinds of methods
+class Spam:
+    @timethis
+    def instance_method(self, n):
+        print(self, n)
+        while n > 0:
+            n -= 1
+
+    @classmethod
+    @timethis
+    def class_method(cls, n):
+        print(cls, n)
+        while n > 0:
+            n -= 1
+
+    @staticmethod
+    @timethis
+    def static_method(n):
+        print(n)
+        while n > 0:
+            n -= 1
+
+from abc import ABCMeta, abstractmethod
+class A(metaclass=ABCMeta):
+    @classmethod
+    @abstractmethod
+    def method(cls):
+        pass

source/c09/p10_apply_decorators_to_class_and_static_methods.rst

@@ -5,14 +5,112 @@
 ----------
 问题
 ----------
-todo...
+你想给类或静态方法提供装饰器。
+
+|
 
 ----------
 解决方案
 ----------
-todo...
+给类或静态方法提供装饰器是很简单的，不过要确保装饰器在 ``@classmethod`` 或 ``@staticmethod`` 之前。例如：
+
+.. code-block:: python
+
+    import time
+    from functools import wraps
+
+    # A simple decorator
+    def timethis(func):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            start = time.time()
+            r = func(*args, **kwargs)
+            end = time.time()
+            print(end-start)
+            return r
+        return wrapper
+
+    # Class illustrating application of the decorator to different kinds of methods
+    class Spam:
+        @timethis
+        def instance_method(self, n):
+            print(self, n)
+            while n > 0:
+                n -= 1
+
+        @classmethod
+        @timethis
+        def class_method(cls, n):
+            print(cls, n)
+            while n > 0:
+                n -= 1
+
+        @staticmethod
+        @timethis
+        def static_method(n):
+            print(n)
+            while n > 0:
+                n -= 1
+
+装饰后的类和静态方法可正常工作，只不过增加了额外的计时功能：
+
+.. code-block:: python
+
+    >>> s = Spam()
+    >>> s.instance_method(1000000)
+    <__main__.Spam object at 0x1006a6050> 1000000
+    0.11817407608032227
+    >>> Spam.class_method(1000000)
+    <class '__main__.Spam'> 1000000
+    0.11334395408630371
+    >>> Spam.static_method(1000000)
+    1000000
+    0.11740279197692871
+    >>>
+
+|
 
 ----------
 讨论
 ----------
-todo...
+如果你把装饰器的顺序写错了就会出错。例如，假设你像下面这样写：
+
+.. code-block:: python
+
+    class Spam:
+        @timethis
+        @staticmethod
+        def static_method(n):
+            print(n)
+            while n > 0:
+                n -= 1
+
+那么你调用这个镜头方法时就会报错：
+
+.. code-block:: python
+
+    >>> Spam.static_method(1000000)
+    Traceback (most recent call last):
+    File "<stdin>", line 1, in <module>
+    File "timethis.py", line 6, in wrapper
+    start = time.time()
+    TypeError: 'staticmethod' object is not callable
+    >>>
+
+问题在于 ``@classmethod`` 和 ``@staticmethod`` 实际上并不会创建可直接调用的对象，
+而是创建特殊的描述器对象(参考8.9小节)。因此当你试着在其他装饰器中将它们当做函数来使用时就会出错。
+确保这种装饰器出现在装饰器链中的第一个位置可以修复这个问题。
+
+当我们在抽象基类中定义类方法和静态方法(参考8.12小节)时，这里讲到的知识就很有用了。
+例如，如果你想定义一个抽象类方法，可以使用类似下面的代码：
+
+.. code-block:: python
+
+    from abc import ABCMeta, abstractmethod
+    class A(metaclass=ABCMeta):
+        @classmethod
+        @abstractmethod
+        def method(cls):
+            pass
+
+在这段代码中，``@classmethod`` 跟 ``@abstractmethod`` 两者的顺序是有讲究的，如果你调换它们的顺序就会出错。