python函数装饰器、类装饰器和带参数的装饰器——装饰器模式

装饰器模式：

动态地给对象添加一些额外的职责，就增加功能来说，装饰模式比生产子类更加灵活
Component 是定义一个对象接口，可以给这些对象动态地添加职责。concreteComponent是定义一个具体对象，也可以给这个对象添加一些职责。decorator，装饰抽象类，继承
l component，从外类来扩展component类的功能，但对于component来说，是无需知道decorator存在的，至于concretedecorator就是具体的装饰对象，起到给component添加职责的功能

python 函数装饰器

import time


def dumpy_decorator(f):
    def wrap_f(*args):
        print("*" * 44)
        print('Function to be decorated:', f.__name__)
        print('nested wrapping function: ', wrap_f.__name__)
        print("*" * 44)
        print("ProfilingDecorator called")
        start_time = time.time()
        resutl = f(*args)
        end_time = time.time()
        print(f"""{end_time-start_time} elapsed""")
        print("ProfilingDecorator called over")
        return resutl
    print('s')
    # wrap_f.__name__=f.__name__
    # wrap_f.__doc__=wrap_f.__doc__
    return wrap_f


@dumpy_decorator
def fib(n):
    print('inside fib')
    if n < 2:
        return
    fibprev = 1
    fib = 1
    for num in range(2, n):
        fibprev, fib = fib, fibprev + fib
    return fib


if __name__ == '__main__':
    print('wrapped function:', fib.__name__)
    res = fib(77)
    print(res)

结果

此函数装饰器导致函数的元信息改变
python标准库包含了一个模块，它允许保留__doc__和__name__的值不被改变
修改：

import time
from functools import wraps


def dumpy_decorator(f):
    @wraps(f)
    def wrap_f(*args):
        print("*" * 44)
        print('Function to be decorated:', f.__name__)
        print('nested wrapping function: ', wrap_f.__name__)
        print("*" * 44)
        print("ProfilingDecorator called")
        start_time = time.time()

结果：

python 类装饰器

import time


class ProfilingDecorator():
    def __init__(self, f):
        print('ProfilingDecorator  initiated')
        self.f = f

    def __call__(self, *args, **kwargs):
        print("ProfilingDecorator called")
        start_time = time.time()
        resutl = self.f(*args)
        end_time = time.time()
        print(f"""{end_time-start_time} elapsed""")
        print("ProfilingDecorator called over")
        return resutl

class ToHTMLDecorator():
    def __init__(self,f):
        print('html decorated inited')
        self.f=f

    def __call__(self, *args, **kwargs):
        print('html decorated called')
        res=self.f(*args)
        print('html decorated over')
        return "{}".format(res)



@ToHTMLDecorator
@ProfilingDecorator
def fib(n):
    print('inside fib')
    if n < 2:
        return
    fibprev = 1
    fib = 1
    for num in range(2, n):
        fibprev, fib = fib, fibprev + fib
    return fib


if __name__ == '__main__':
    n = 77
    res = fib(n)

    print(f'''the result is {res}''')

结果：

带参数的装饰器

from functools import wraps
import time


def profiling_decorator_with_unit(unit):
    def profile_decorator(f):
        @wraps(f)
        def wrap_f(*args):
            start_time = time.time()
            resutl = f(*args)
            end_time = time.time()
            if unit == 'seconds':
                print(f"""{(end_time - start_time)/1000} elapsed""")
            else:
                print(f"""{(end_time - start_time) } elapsed""")
            return resutl
        return wrap_f
    return profile_decorator


@profiling_decorator_with_unit('else')
def fib(n):
    print('inside fib')
    if n < 2:
        return
    fibprev = 1
    fib = 1
    for num in range(2, n):
        fibprev, fib = fib, fibprev + fib
    return fib


if __name__ == '__main__':
    res = fib(77)
    print(res)