迭代器/生成器/装饰器,3个知识点搞定Python神仙代码!

>>> from collections import Iterable>>> isinstance([], Iterable)True

>>> from collections import Iterator>>> isinstance((x for x in range(10)), Iterator)True>>> isinstance([], Iterator)False

>>> isinstance(iter([]), Iterator)True>>> isinstance(iter('abc'), Iterator)True

class MyNumbers:  def __iter__(self):    self.a = 1    return self  def __next__(self):    if self.a <= 20:      x = self.a      self.a += 1      return x    else:      raise StopIterationmyclass = MyNumbers()myiter = iter(myclass)for x in myiter:  print(x)

>>> L = [x * x for x in range(10)]>>> L[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]>>> G = (x * x for x in range(10))>>> G<generator object <genexpr> at 0x000000D25E141B88>>>> G.next()Traceback (most recent call last):  File "<stdin>", line 1, in <module>AttributeError: 'generator' object has no attribute 'next'>>> G.__next__()0>>> G.__next__()1>>> G.__next__()4>>> G.__next__()9>>> G.__next__()16>>> G.__next__()25>>> G.__next__()36>>> G.__next__()49>>> G.__next__()64>>> G.__next__()81>>> G.__next__()Traceback (most recent call last):  File "<stdin>", line 1, in <module>StopIteration

>>> G = (x * x for x in range(10))>>> for e in G:...     print(e)...0149162536496481

>>> def fibonacci(end):...     a, b, c = 0, 0, 1...     while a < end:...             print(c)...             b, c = c, b+c...             a = a+1...>>> fibonacci(10)11235813213455>>>

>>> def fibonacci(end):...     a, b, c = 0,0,1...     while a < end:...             yield(c)...             b,c = c, b+c...             a=a+1...>>> fibonacci(10)<generator object fibonacci at 0x000000D25E2792A0>>>> num = fibonacci(10)>>> num.__next__()1>>> num.__next__()1>>> num.__next__()2>>> num.__next__()3>>> num.__next__()5>>> for i in fibonacci(10):...     print(i)...11235813213455

>>> def print_name(name='davieyang'):...     return name...

>>> print(print_name)<function print_name at 0x0000000CB357C268>>>> print(print_name())davieyang>>> print(print_name.__name__)print_name>>>

>>> print_func = print_name>>> print_func_f = print_name()>>> print(print_func)<function print_name at 0x0000000CB357C268>>>> print(print_func_f)davieyang>>> print(print_func())davieyang

>>> del print_name>>> print(print_name)Traceback (most recent call last):  File "<stdin>", line 1, in <module>NameError: name 'print_name' is not defined>>> print(print_name())Traceback (most recent call last):  File "<stdin>", line 1, in <module>NameError: name 'print_name' is not defined>>> print(print_func)<function print_name at 0x0000000CB357C268>>>> print(print_func())davieyang>>> print(print_func_f())Traceback (most recent call last):  File "<stdin>", line 1, in <module>TypeError: 'str' object is not callable>>> print(print_func_f)davieyang

>>> def print_name(name='davieyang'):...     print("currently, you are inside the print_name() function")...     def say_hello():...             return "currently, you are inside the say_hello() function"...     def say_goodbye():...             return "currently, you are inside the say_goodbye() function"...     print(say_hello())...     print(say_goodbay())...     print("currently, you are back in the print_name() function")...>>> print_name()currently, you are inside the print_name() functioncurrently, you are inside the say_hello() functioncurrently, you are inside the say_goodbye() functioncurrently, you are back in the print_name() function>>> say_hello()Traceback (most recent call last):  File "<stdin>", line 1, in <module>NameError: name 'say_hello' is not defined>>>

>>> def print_name(name='davieyang'):...             print("currently, you are inside the print_name() function")...     def say_hello():...             return "currently, you are inside the say_hello() function"...     def say_goodbye():...             return "currently, you are inside the say_goodbye() function"...     if name == "davieyang":...             return say_hello...     else:...             return say_goodbye...     print(say_hello())...     print(say_goodbay())...     print("currently, you are back in the print_name() function")...>>> a = print_name()>>> print(a)<function say_hello at 0x7f2143c01500>

>>> def print_name(name='davieyang'):...             print("currently, you are inside the print_name() function")...>>> def  do_something_before_print_name(func):...             print("for doing something before executing print_name()")...             print(func())...>>> do_something_before_print_name(print_name)for doing something before executing print_name()currently, you are inside the print_name() function

def a_new_decorator(a_func):    def wrapTheFunction():        print("I am doing some boring work before executing a_func()")        a_func()        print("I am doing some boring work after executing a_func()")    return wrapTheFunctiondef a_function_requiring_decoration():    print("I am the function which needs some decoration to remove my foul smell")a_function_requiring_decoration()#outputs: "I am the function which needs some decoration to remove my foul smell"a_function_requiring_decoration = a_new_decorator(a_function_requiring_decoration)#now a_function_requiring_decoration is wrapped by wrapTheFunction()a_function_requiring_decoration()#outputs:I am doing some boring work before executing a_func()#        I am the function which needs some decoration to remove my foul smell#        I am doing some boring work after executing a_func()

@a_new_decoratordef a_function_requiring_decoration():    """Hey you! Decorate me!"""    print("I am the function which needs some decoration to "          "remove my foul smell")a_function_requiring_decoration()#outputs: I am doing some boring work before executing a_func()#         I am the function which needs some decoration to remove my foul smell#         I am doing some boring work after executing a_func()

@a_new_decorator代替了a_function_requiring_decoration=a_new_decorator(a_function_requiring_decoration)

>>> print(a_function_requiring_decoration.__name__)wrapTheFunction

from functools import wrapsdef a_new_decorator(a_func):    @wraps(a_func)    def wrapTheFunction():        print("I am doing some boring work before executing a_func()")        a_func()        print("I am doing some boring work after executing a_func()")    return wrapTheFunction@a_new_decoratordef a_function_requiring_decoration():    """Hey yo! Decorate me!"""    print("I am the function which needs some decoration to "          "remove my foul smell")>>> print(a_function_requiring_decoration.__name__)a_function_requiring_decoration

class logit:    _logfile = 'out.log'    def __init__(self, func):        self.func = func    def __call__(self, *args):        log_string = self.func.__name__ + " was called"        print(log_string)        # Open the logfile and append        with open(self._logfile, 'a') as opened_file:            # Now we log to the specified logfile            opened_file.write(log_string + '\n')        # Now, send a notification        self.notify()        # return base func        return self.func(*args)    def notify(self):        # logit only logs, no more        pass

logit._logfile = 'out2.log' @logitdef myfunc():    passmyfunc()# Output: myfunc1 was called

class email_logit(logit):    '''    Let’s subclass logit to add email functionality, from here, @email_logit works just like @logit but sends an email to the admin in addition to logging.    A logit implementation for sending emails to admins    when the function is called.    '''    def __init__(self, email='admin@myproject.com', *args, **kwargs):        self.email = email        super(email_logit, self).__init__(*args, **kwargs)    def notify(self):        # Send an email to self.email        # Will not be implemented here        pass

import loggingfrom selenium import webdriverfrom time import sleepclass DecoratorDemo:    def __init__(self, func):        self.func = func    def __call__(self, *args, **kwargs):        driver = webdriver.Chrome()        driver.get(url="http://www.baidu.com")        logging.warning("%s is running" % self.func.__name__)        self.notify()        return self.func(*args, **kwargs)    def notify(self):        print(self.notify.__name__ + " " + "was called....")@DecoratorDemodef test_access_baidu():    print("Baidu website is opened...")    sleep(5)if __name__ == '__main__':    test_access_baidu()

# -*- coding: utf-8 -*-import loggingimport unittestfrom functools import wrapsfrom selenium import webdriver"""被装饰的函数有可能是不带参数的，有可能是带参数的，装饰器应如何编写"""def starting_browser_none_parameter(func):    """    starting_browser_none_parameter是一个装饰器，返回函数wrap_starting_browser    函数的进入和退出时，被称为一个横切面，这种编程方式被称为面向切面编程    """    @wraps(func)    def wrap_starting_browser():        driver = webdriver.Chrome()        driver.get(url="http://www.baidu.com")        logging.warning("%s is running" % func.__name__)        return func()    return wrap_starting_browserdef starting_browser_with_simple_parameter(func):    """    starting_browser是一个装饰器，返回一个函数    """    @wraps(func)    def wrap_starting_browser(self):        """        函数的参数定义是(*args, **kwargs)，因此，wrap_starting_browser()函数可以接受任意参数的调用。        """        driver = webdriver.Chrome()        driver.get(url="http://www.baidu.com")        logging.warning("%s is running" % func.__name__)        return func(self)    return wrap_starting_browserdef starting_browser_with_sophisticated_parameter(func):    @wraps(func)    def wrap_starting_browser(*args, **kwargs):        """        函数的参数定义是(*args, **kwargs)，因此，wrap_starting_browser()函数可以接受任意参数的调用。        *args是一个数组，**kwargs是一个字典        """        driver = webdriver.Chrome()        driver.get(url="http://www.baidu.com")        logging.warning("%s is running" % func.__name__)        return func(*args, **kwargs)    return wrap_starting_browserclass TestDecorator(unittest.TestCase):    @starting_browser_with_simple_parameter    def test_access_baidu(self):        print("Baidu website is opened...")

# -*- coding: utf-8 -*-import loggingimport unittestfrom functools import wrapsfrom selenium import webdriver"""装饰器还有更大的灵活性，例如带参数的装饰器，在上面的装饰器调用中，该装饰器接收唯一的参数就是执行业务的函数装饰器的语法允许我们在调用时，提供其它参数，比如@decorator(parameter)。这样，就为装饰器的编写和使用提供了更大的灵活性比如，我们可以在装饰器中指定日志的等级，因为不同业务函数可能需要的日志级别是不一样的它实际上是对原有装饰器的一个函数封装，并返回一个装饰器。我们可以将它理解为一个含有参数的闭包当我 们使用@starting_browser_with_parameter(browser_name='firefox')调用的时候Python 能够发现这一层的封装，并把参数传递到装饰器的环境中"""def starting_browser_with_parameter(browser_name):    def decorator_with_parameter(func):        @wraps(func)        def wrap_starting_browser(*args, **kwargs):            if browser_name.lower() == 'chrome':                driver = webdriver.Chrome()                driver.get(url="http://www.baidu.com")                logging.warning("%s is running" % func.__name__)            elif browser_name.lower() == 'firefox':                driver = webdriver.Firefox()                driver.get(url="http://www.baidu.com")                logging.warning("%s is running" % func.__name__)            else:                driver = webdriver.Ie()                driver.get(url="http://www.baidu.com")                logging.warning("%s is running" % func.__name__)            return func(*args, **kwargs)        return wrap_starting_browser    return decorator_with_parameterclass TestDecorator(unittest.TestCase):    @starting_browser_with_parameter(browser_name='firefox')    def test_access_baidu(self):        print("Baidu website is opened...")