Python
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10.2 装饰器使用的形式
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- 嵌套使用装饰器
- 不带参数的装饰器
- 带参数的装饰器
嵌套使用装饰器
@decor1
@decor2
@decor3
def hello(name):
print(name)
注意装饰顺序, 距离被装饰函数越近的越先调用, 效果等同于
hello = decor1(decor2(decor3(hello)))
嵌套使用装饰器的例子:
def decor1(f):
def wrapper(name):
print("Hello from decor1")
f(name)
return wrapper
def decor2(f):
def wrapper(name):
print("Hello from decor2")
f(name)
return wrapper
def decor3(f):
def wrapper(name):
print("Hello from decor3")
f(name)
return wrapper
@decor1
@decor2
@decor3
def hello(name):
print("Hello,", name)
hello(Zhang San)
不带参数的装饰器
我们前面举得例子基本是不带参数的
带参数与不带参数的装饰器比较
- 不带参数
@hello_decor
def hello(name):
print("How are you? {}".format(name))
相当于
def hello(name):
print("How are you? {}".format(name))
hello = hello_decor(hello)
- 带参数
@repeat_hello_decor(3)
def hello(name):
print("How are you? {}".format(name))
相当于
def hello(name):
print("How are you? {}".format(name))
hello = repeat_hello_decor(3)(hello)
带参数的装饰器
def repeat_hello_decor(number):
def wrapper(f):
def proxy(name):
print("Inside proxy")
for x in range(number):
f(name)
return proxy
return wrapper
@decor(3)
def hello(name):
print("Hello", name)
参数number控制hello函数执行的次数
注意：带参数的装饰器在装饰时是带扩招的，不带参数的则没有括号
练习
实现一个装饰器，其对下面给定函数的执行时间进行统计，统计其执行了多少秒。运行时间打印出来即可。
def func():
print("Inside func")
print("Running ....")
for i in range(5):
print("Counting {}".format(i))
time.sleep(0.5)
print("Exit func")
给这个装饰器增加一个参数，用来指定func函数运行的次数。算出平均执行时间。把运行次数和平均运行时间打印出来。
解答
def wrapper(func):
def cal():
t1 = time.time()
func()
delta = time.time()-t1
print("time consuming {}".format(delta))
return cal
@wrapper
def func():
print("Inside func")
print("Running ....")
for i in range(5):
print("Counting {}".format(i))
time.sleep(0.5)
print("Exit func")
import time
func()
执行结果
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.501143217086792
如果添加执行次数参数，代码修改如下
def wrapper_param(times):
def wrapper(func):
def cal():
consumed = 0
for i in range(times):
t1 = time.time()
func()
delta = time.time()-t1
consumed = consumed + delta
print("time consuming {}".format(delta))
ave_consumed = consumed / times
print("run {} times, average time consuming {}".format(times, ave_consumed))
return cal
return wrapper
@wrapper_param(10)
def func():
print("Inside func")
print("Running ....")
for i in range(5):
print("Counting {}".format(i))
time.sleep(0.5)
print("Exit func")
import time
func()
执行结果如下
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.501143217086792
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.500142812728882
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.501142978668213
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.500143051147461
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.500142812728882
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.50014328956604
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.500142812728882
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.506143569946289
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.500142812728882
Inside func
Running ....
Counting 0
Counting 1
Counting 2
Counting 3
Counting 4
Exit func
time consuming 2.500143051147461
run 10 times, average time consuming 2.5009430408477784