装饰器02

1 装饰器的语法糖

1.1 定义

为了简洁而优雅地使用装饰器，Python提供了专门的装饰器语法来取代index=timer(index)的形式，需要在被装饰对象的正上方单独一行添加@timer,当解释器解释到@timer时就会调用timer函数，且把它正下方的函数名当做实参传入，然后将返回的结果重新赋值给原函数名

1.2 基本使用

import time

def timmer(f):
    def wrapper(*args,**kwargs):
        start = time.time()
        res = f(*args,**kwargs)
        stop = time.time()
        print('run time is %s' % (stop - start))
        return res
    return wrapper


@timmer  # index = timmer(index)
def index():
    time.sleep(1)
    print('from index')


@timmer  # home = time(home)
def home(name):
    time.sleep(2)
    print('welcome to %s' % name)
    return 123


index()
res = home("ccc")
print(res) 

# from index
# run time is 1.0003390312194824

# welcome to ccc
# run time is 2.0008108615875244
# 123

2 有参装饰器

2.1 基本用法

@auth(driver='file') 
def index():     
    pass
@auth(driver='mysql') 
def home():
    pass 

2.2 示例

import time

def login(x,engine='file'):
    def auth(func):
        def wrapper(*args,**kwargs):
            print("========>",x)
            inp_user = input("username>>>>:").strip()
            inp_pwd = input("password>>>:").strip()

            if engine == "file":
                print("基于file认证")
                if inp_user == "egon" and inp_pwd == "123":
                    print('login successful')
                    res = func(*args,**kwargs)
                    return res
                else:
                    print('username or password error')
            elif engine == 'mysql':
                print("基于mysql认证")
            elif engine == "ldap":
                print("基于ldap认证")
            else:
                print("未知认证来源")
        return wrapper
    return auth


@login(11,engine='file')  # @auth  # index = auth(index)  # index=wrapper
def index():
    time.sleep(1)
    print('from index')


@login(22,engine='file')  # @auth  # home=auth(home)  # home=wrapper
def home(name):
    time.sleep(2)
    print('home page,welcome %s' % name)
    return 123


index()
home('egon')

# ========> 11
# username>>>>:egon
# password>>>:123
# 基于file认证
# login successful
# from index

# ========> 22
# username>>>>:egon
# password>>>:123
# 基于file认证
# login successful
# home page,welcome egon

3叠加多个装饰器

3.1 基本用法

@deco3
@deco2
@deco1
def index():
	pass

# 本质
index=deco3(deco2(deco1(index)))

3.2 示例

def outter1(func1):  # func1 = wrapper2的内存地址
    print('============>outter1')
    def wrapper1(*args,**kwargs):
        print('=============wrapper1')
        res1 = func1(*args,**kwargs)
        return res1
    return wrapper1


def outter2(func2):  # func2 = wrapper3的内存地址
    print('============>outter2')
    def wrapper2(*args,**kwargs):
        print('=============wrapper2')
        res2 = func2(*args,**kwargs)
        return res2
    return wrapper2


def outter3(func3):  # func3 = index的内存地址
    print('============>outter3')
    def wrapper3(*args,**kwargs):
        print('=============wrapper3')
        res3 = func3(*args,**kwargs)
        return res3
    return wrapper3

          # index = wrapper1的内存地址
@outter1  # outter1(wrapper2的内存地址)-->wrapper1的内存地址
@outter2  # outter2(wrapper3的内存地址)-->wrapper2的内存地址
@outter3  # outter3(index的内存地址)-->wrapper3的内存地址
def index():
    print('from index')


print('*'*25)
# print(index)
index()

# ============>outter3
# ============>outter2
# ============>outter1
# *************************
# =============wrapper1
# =============wrapper2
# =============wrapper3
# from index

import time

def timmer(func):
	def wrapper1(*args,**kwargs):
		start = time.time()
		res = func(*args,**kwargs)
		stop = time.time()
		print('run time is:%s' % (stop - start))
		return res
	return wrapper1


def login(x,engine='file'):
	def auth(func):
		def wrapper2(*args,**kwargs):
			print("========>",x)
			inp_user = input("username>>>>:").strip()
			inp_pwd = input("password>>>:").strip()

			if engine == "file":
				print("基于file认证")
			if inp_user == "egon" and inp_pwd == "123":
				print('login successful')
				res = func(*args,**kwargs)
				return res
			else:
				print('username or password error')
			elif engine == 'mysql':
				print("基于mysql认证")
			elif engine == "ldap":
				print("基于ldap认证")
			else:
				print("未知认证来源")
		return wrapper2
	return auth


# 场景一
@timmer
@login(11,engine='file')
def index():
	time.sleep(1)
	print('from index')


index()

# ========> 11
# username>>>>:egon
# password>>>:123
# 基于file认证
# login successful
# from index
# run time is:9.147817134857178


# 场景二
@login(11,engine='file')
@timmer
def index():
	time.sleep(1)
	print('from index')


index()

# ========> 11
# username>>>>:egon
# password>>>:123
# 基于file认证
# login successful
# from index
# run time is:1.0001623630523682

4 wraps装饰器

4.1 定义

• functools模块下提供一个装饰器wraps专门用来帮我们保留原函数的文档和函数名属性，修正装饰器

4.2 示例

import time
from functools import wraps


def timmer(func):
    @wraps(func)
    def wrapper(*args,**kwargs):
        start = time.time()
        res = func(*args,**kwargs)
        stop = time.time()
        print('run time is:%s' % (stop - start))
        return res
    return wrapper


@ timmer
def index():
    """index函数"""
    time.sleep(1)
    print('from index')


help(index)

5 匿名函数

"""
def func(x,y):  # func=函数的内存地址
    return x+y

匿名函数:没有名字的函数
应用场景:临时用一次，通常用于与其他函数配合使用
"""

# 无用调用方式
f = lambda x,y: x+y
print(f)
res = f(1,2)
print(res)

# 调用方式1
res = (lambda x,y: x+y)(1,2)
print(res)

# 调用方式2
salaries = {
    "egon": 1000,"alex": 2000,"jack": 3000,"rose": 4000
}
# 求薪资最高的那个人的名字

def get_salary(name):
    return salaries[name]

print(max(salaries,key = get_salary))  # rose
print(max(salaries,key=lambda name: salaries[name]))  # rose
print(min(salaries,key=lambda name: salaries[name]))  # egon
print(sorted(salaries))  # ['alex','egon','jack','rose']
print(sorted(salaries,key=lambda name: salaries[name]))  # ['egon','alex',key=lambda name: salaries[name],reverse=True))  # ['rose','egon']

# 返回绝对值
print(abs(-11))  # 11
print(abs(0))  # 0
print(abs(11))  # 11

# 如果是空或布尔值为真则返回True
print(all(''))  # True
print(all([]))  # True
print(all([11,22,333,0]))  # False

# 只要有一个值的布尔值为真就返回True
print(any(''))  # False
print(any([]))  # False
print(any([0,None,'',1]))  # True
print(any([0,'']))  # False

# ASCⅡ表:65-90 A-Z
print(chr(65))  # 数字->字母A
print(ord('A'))  # 字母->数字65
print(chr(90))  # Z

# 进制转换
print(bin(11))  # 十进制->二进制 0b1011
print(oct(11))  # 十进制->八进制 0o13
print(hex(11))  # 十进制->十六进制 0xb

# 工厂函数
int
float
str
list
tuple
dict
set
bool
bytes

# 查看对象是否可调用
print(callable(len))  # True

# 面向对象重点
classmethod
staticmethod
setattr
getattr
delattr
hasattr
dir
exec

l = eval("[1,2,3]")
print(l[0])  # 1
with open('user1.txt',mode='wt',encoding='utf-8') as f:
    dic = {"ccc": "123","zzz": "456","yyy": "789"}
    f.write(str(dic))

with open('user1.txt',mode='rt',encoding='utf-8') as f:
    data = f.read()
    print(data,type(data))  # {'ccc': '123','zzz': '456','yyy': '789'} <class 'str'>
    dic = eval(data)
    print(dic["ccc"])  # 123

（编辑：李大同）

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