【脚本语言系列】关于Python基础知识装饰器，你需要知道的事

如何使用装饰器(Decorators)

• 知识准备

  • 对象复制

# -*- coding:utf-8 -*-def hello(name = "AllenMoore"):    return "Hello " + nameprint hello()greet = helloprint greet()del helloprint hello()

Hello AllenMooreHello AllenMooreHello AllenMoore---------------------------------------------------------------NameError                     Traceback (most recent call last)<ipython-input-6-8d0abdde1ee5> in <module>()     10 del hello     11 print greet()---> 12 print hello()NameError: name 'hello' is not defined* __函数内嵌函数__

# -*- coding:utf-8 -*-def hello(name = "AllenMoore"):    print "Now You are hello out."    def hi():        return "Now You are hi."    def bye():        return "Now You are bye."    print hi()    print bye()    print "Now you are hello in."hello()hi()

Now You are hello out.Now You are hi.Now You are bye.Now you are hello in.---------------------------------------------------------------NameError                     Traceback (most recent call last)<ipython-input-9-ec0e2edbd16b> in <module>()     16      17 hello()---> 18 hi()NameError: name 'hi' is not defined* __函数作为返回值__

# -*- coding:utf-8 -*-def hello(name = "AllenMoore"):    def hi():        return "Now You are hi."    def bye():        return "Now You are bye."    if name == "AllenMoore":        return hi    else:        return byethe_greet = hello()print the_greetprint the_greet()

* __函数作为参数__

# -*- coding:utf-8 -*-def hello():    return "Now You are hello."def doSthAhead(func):    print "do something ahead."    print func()doSthAhead(hello)

• 装饰器

  • 简单的装饰器

# -*- coding:utf-8 -*-def the_new_decorator(a_func):    def wrap_the_func():        print "Before exec the func, I do sths."        a_func()        print "After exec the func, I do sths."    return wrap_the_funcdef the_func_needDecoration():    print "Here We need some decoration."the_func_needDecoration()the_func_needDecoration = the_new_decorator(the_func_needDecoration)the_func_needDecoration()

Here We need some decoration.Before exec the func, I do sths.Here We need some decoration.After exec the func, I do sths.

# -*- coding:utf-8 -*-def the_new_decorator(a_func):    def wrap_the_func():        print "Before exec the func, I do sths."        a_func()        print "After exec the func, I do sths."    return wrap_the_func@the_new_decoratordef the_func_needDecoration():    print "Here We need some decoration."the_func_needDecoration()the_func_needDecoration = the_new_decorator(the_func_needDecoration)print the_func_needDecoration.__name__

Before exec the func, I do sths.Here We need some decoration.After exec the func, I do sths.wrap_the_func

# -*- coding:utf-8 -*-from functools import wrapsdef the_new_decorator(a_func):    def wrap_the_func(a_func):        print "Before exec the func, I do sths."        a_func()        print "After exec the func, I do sths."    return wrap_the_func@the_new_decoratordef the_func_needDecoration():    """Decorater the func!"""    print "Here We need some decoration."the_func_needDecoration()the_func_needDecoration = the_new_decorator(the_func_needDecoration)print the_func_needDecoration.__name__

---------------------------------------------------------------TypeError                     Traceback (most recent call last)<ipython-input-40-1349141083db> in <module>()     12     print "Here We need some decoration."     13 ---> 14 the_func_needDecoration()     15 the_func_needDecoration = the_new_decorator(the_func_needDecoration)     16 print the_func_needDecoration.__name__TypeError: wrap_the_func() takes exactly 1 argument (0 given)

- __含参数的装饰器__

- __嵌入函数的装饰器__

# -*- coding:utf-8 -*-from functools import wrapsdef logit(logfile='out.log'):    def logging_decorator(func):        @wraps(func)        def wrapped_function(*args, **kwargs):            log_string = func.__name__ + " just called"            print log_string            with open(logfile, 'a') as opened_file:                opened_file.write(log_string + '\n')        return wrapped_function    return logging_decorator@logit()def the_func1():    passthe_func()@logit(logfile='func2.log')def the_func2():    passthe_func1()the_func2()

the_func just calledthe_func1 just calledthe_func2 just called

• 装饰器类

# -*- coding:utf-8 -*-# Only for Python 2.xclass logit(object):    def __init__(self, logfile='out.log'):        self.logfile = logfile    def __call__(self, func):        log_string = func.__name__ + " just called"        print log_string        with open(self.logfile, 'a') as opened_file:            opened_file.write(log_string + '\n')        self.notify()    def notify(self):        pass@logit()def the_func1():    passclass email_logit(logit):    '''When call the function, send email to the manager.'''    def __init__(self, email = '[e-mail]', *args, **kwargs):        self.email = email        super(logit, self).__init__(*args, **kwargs)    def notify(self):        pass@email_logit()def the_func2():    passthe_func1()the_func2()

the_func1 just calledthe_func2 just called---------------------------------------------------------------AttributeError                Traceback (most recent call last)<ipython-input-34-65071749c9a2> in <module>()     27      28 ---> 29 @email_logit()     30 def the_func2():     31     pass<ipython-input-34-65071749c9a2> in __call__(self, func)      7         log_string = func.__name__ + " just called"      8         print log_string----> 9         with open(self.logfile, 'a') as opened_file:     10             opened_file.write(log_string + '\n')     11         self.notify()AttributeError: 'email_logit' object has no attribute 'logfile'

• 使用场景

  • 模板(Blueprint)

# -*- coding:utf-8 -*-from functools import wrapsdef decorator_func(func):    @wraps(func)    def decorated(*args, **kwargs):        if not do_run:            return "func no run"        return func(*args, **kwargs)    return decorated@decorator_funcdef func():    return "func just run"do_run = Trueprint func()

func just run- __授权(Authorization)__

# -*- coding:utf-8 -*-# Only For Python 2.xfrom functools import wrapsfrom urllib import requestdef requires_auth(func):    @wraps(func)    def decorated(*args, **kwargs):        auth = request.authorization        if not auth or not check_auth(auth.username, auth.password):            authenticate()        return func(*args, **kwargs)    return decorated@requires_authdef auth_func():    return "auth is done."auth_done = auth_func()print auth_done

---------------------------------------------------------------ImportError                   Traceback (most recent call last)<ipython-input-26-27f77c33258d> in <module>()      1       2 from functools import wraps----> 3 from urllib2 import request      4       5 def requires_auth(func):ImportError: cannot import name request- __日志(Logging)__

# -*- coding:utf-8 -*-from functools import wrapsdef logit(func):    @wraps(func)    def with_logging(*args, **kwargs):        print func.__name__ + " just called."        return func(*args, **kwargs)    return with_logging@logitdef addition_func(x):    """Do sth."""    return x + xresult = addition_func(4)print result

addition_func just called.8

什么是装饰器(Decorators)

装饰器是改变其他函数的功能的函数。

为何使用装饰器(Decorators)

装饰器能够使代码更为简洁。