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装饰器的一般语法结构如下：
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```python
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def decorator(func):
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def wrapper():
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# 新增功能或者附加限制条件
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# ...
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return func()
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return wrapper
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```
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装饰器函数可以不用使用装饰器语法糖@，而是采用原始的方式进行调用。例如，下面是一个用于计算函数运行时间的装饰器函数，它的等效写法是：
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```python
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import time
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def my_decorator(func):
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def wrapper(*args, **kwargs):
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start_time = time.time()
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result = func(*args, **kwargs)
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end_time = time.time()
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print("Function took {:.6f} seconds.".format(end_time - start_time))
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return result
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return wrapper
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def my_function(x):
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time.sleep(x)
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return x
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decorated_function = my_decorator(my_function)
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print(decorated_function(2))
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```
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装饰器也可以用类进行实现，我们可以定义一个类，将需要被装饰的函数作为一个参数传递给类的构造函数，并重载类的__call__方法。
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例如，下面是一个用于计算函数运行时间的类装饰器，它的等效写法是：
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```python
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import time
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class MyDecorator:
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def __init__(self, func):
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self.func = func
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def __call__(self, *args, **kwargs):
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start_time = time.time()
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result = self.func(*args, **kwargs)
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end_time = time.time()
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print("Function took {:.6f} seconds.".format(end_time - start_time))
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return result
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@MyDecorator
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def my_function(x):
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time.sleep(x)
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return x
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print(my_function(2))
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```
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### 单参数被装饰函数
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```python
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def my_decorator(func):
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def wrapper(arg):
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print("Calling function...")
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result = func(arg)
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print("Function returned: ", result)
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return result
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return wrapper
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@my_decorator
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def my_function(x):
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return x * 2
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my_function(2) # 输出：Calling function... Function returned: 4
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```
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### 多参数被装饰函数
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```python
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def my_decorator(func):
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def wrapper(*args, **kwargs):
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print("Calling function...")
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result = func(*args, **kwargs)
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print("Function returned: ", result)
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return result
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return wrapper
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@my_decorator
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def my_function(x, y, z):
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return x + y + z
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my_function(2, 3, z=4) # 输出：Calling function... Function returned: 9
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``` |
