装饰器学习

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定义：本质是函数，（装饰其他函数）就是为其他函数添加附加功能

原则：1.不能修改被装饰的函数的源代码

2.不能修改被装饰的函数的调用方式

实现装饰器知识储备：

1．函数即“变量”，函数在调用前需要先声明

2. 高阶函数

a：把一个函数名当作实参传递给另外一个函数（在不修改被装饰函数情况下为其增加功能）

def test1():

print('in the test1')

def test2(func): # func = test1

res = func() # func() = test1()

return res

test2(test1)

结果：in the test1

b：返回值中包含函数名（不修改函数的调用方式）

def test1():

print('in the test1')

def test2(func): # func = test1

return func

test1 = test2(test1)

test1()

结果：in the test1

3. 嵌套函数：在一个函数内声明一个函数

def test1():

def test2():

print("in the test2")

test2()

test1()

结果：in the test2

内嵌函数的作用在函数内部，不可以在外部进行调用，如下面则是错误的：

def test1():

def test2():

print("in the test2")

test1()

test2() # 该函数作用域在函数test1内部，超出该范围则会报错

结果：NameError: name 'test2' is not defined

如果在函数内部有和函数外部同名变量，优先访问内部变量

def test1():

x = 1

def test2():

x = 2

def test3():

x = 3

print(x)

test3()

test2()

test1()

结果：3

高级函数 + 嵌套函数 =》装饰器

1. 无参数

Import time

def decorartor(func):

def wrapper():

start_time = time.time()

func()

stop_time = time.time()

print("the func run time is % s" % (stop_time - start_time))

return wrapper

def test1():

time.sleep(3)

print('in the test1')

print(decorartor(test1))

结果：<function decorartor.<locals>.wrapper at 0x000000000270AA60>

上面decorartor(test1) 得到的是 wrapper函数体存放的地址空间，想要进行执行并的到结果，可以如下操作：

test1 = decorartor(test1)

test1()

# 或decorartor(test1)()

结果：

in the test1

the func run time is 3.0137999057769775

2.固定参数

import time

def decorartor(func):

def wrapper(n):

start_time = time.time()

func(n)

stop_time = time.time()

print("the func run time is % s" % (stop_time - start_time))

return wrapper

def test1(n):

time.sleep(3)

print('in the test1 n is %s' % n)

#decorartor(test1)(10)

test = decorartor(test1)

test(10)

结果：

in the test1 n is 10

the func run time is 3.0138003826141357

3. 不定参数

import time

def decorartor(func):

def wrapper(*args, **kwargs):

start_time = time.time()

func(*args, **kwargs)

stop_time = time.time()

print("the func run time is % s" % (stop_time - start_time))

return wrapper

def test1(n):

time.sleep(3)

print('in the test1 n is %s' % n)

def test2(n, m):

time.sleep(3)

print('in the test1 n is %s, m is %s' % (n, m))

decorartor(test1)(10)

decorartor(test2)(10, 100)

结果：

in the test1 n is 10

the func run time is 3.012200117111206

in the test1 n is 10, m is 100

the func run time is 3.000199794769287

4. 无参装饰器

import time

def decorartor(func):

def wrapper(*args, **kwargs):

start_time = time.time()

func(*args, **kwargs)

stop_time = time.time()

print("the func run time is % s" % (stop_time - start_time))

return wrapper

@decorartor # 相当于 test1 = decorartor(test1)

def test1():

time.sleep(3)

print('in the test1 ')

@decorartor # 相当于 test2 = decorartor(test2)

def test2(n, m):

time.sleep(3)

print('in the test1 n is %s, m is %s' % (n, m))

test1()

test2(10, 100)

结果：

in the test1

the func run time is 3.0

in the test1 n is 10, m is 100

the func run time is 3.0

5. 有参装饰器

import time

def timer(timeout = 0):

def decorartor(func):

def wrapper(*args, **kwargs):

start_time = time.time()

func(*args, **kwargs)

stop_time = time.time()

print("the func run time is % s" % (stop_time - start_time))

if (stop_time - start_time) > timeout:

print("程序运行超时")

return wrapper

return decorartor

@timer(2) # 相当于 test1 = decorartor(test1)

def test1():

time.sleep(3)

print('in the test1')

@timer(5) # 相当于 test2 = decorartor(test2)

def test2(n, m):

time.sleep(3)

print('in the test1 n is %s, m is %s' % (n, m))

test1()

test2(10, 100)

结果：

in the test1

the func run time is 3.0

程序运行超时

in the test1 n is 10, m is 100

the func run time is 3.0

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