Python基础 装饰器

装饰器(decorator)

1. 函数基础

   # function.py  函数
   # 1）函数是对象
   def hello():
       return 'Hello, world!'
   
   func = hello
   print(func)  # <object>
   print(func())
   
   
   # 2）函数可以嵌套，定义在另一个函数内部
   def show():
       print('Run in show()')
       def message(word='Hello'):
           return word
       print(message())
   
   show()
   
   
   # 3）函数作为参数返回
   def getWordType(kind=''):
       def default(word=''):
           return word
       def upper(word=''):
           return word.upper()
       def lower(word=''):
           return word.lower()
   
       if kind.lower() == 'lower':
           return lower
       elif kind.lower() == 'upper':
           return upper
       else:
           return default
   
   wordType = getWordType('upper')
   print(wordType)
   print(wordType('Resistance is futile!'))
   
   
   # 4）函数作为参数传入
   def getName(name='leo'):
       return name
   
   def foo(func):
       print('I will call the getName function later')
       print(func())
   
   foo(getName)

2. 装饰器以及函数比较

   # decorator.py  装饰器
   # 不使用装饰器情况
   def my_new_decorator(a_function_to_decorator):
       def the_wrapper_around_the_original_function():
           print('Befor the function runs')
           a_function_to_decorator()
           print('After the function runs')
       return the_wrapper_around_the_original_function  # 将函数作为参数返回
   
   
   def a_stand_alone_function():
       print("I'm a stand alone function, don't you dare modify me.")
   
   
   a_stand_alone_function()
   a_stand_alone_function_decorated = my_new_decorator(a_stand_alone_function)  # 将函数作为参数传入
   print(a_stand_alone_function_decorated)
   a_stand_alone_function_decorated()
   
   # 使用装饰器 语法糖"@"
   @my_new_decorator
   def another_stand_alone_function():
       print('leave me alone')
   
   
   another_stand_alone_function()
   # same as: another_stand_alone_function = my_new_decorator(another_stand_alone_function)
3. 装饰器应用

   # decorator_web.py  web中的装饰器应用
   def makebold(func):
       def wrapper():
           return '<b>' + func() + '</b>'
       return wrapper
   
   def makeitalic(func):
       def wrapper():
           return '<i>' + func() + '</i>'
       return wrapper
   
   @makebold
   @makeitalic
   def word():
       return 'Hello, decorator!'
   
   
   print(word())

   # decorator_time.py  使用装饰器检查函数的运行时间
   import time
   import os
   
   
   def timer(func):
       def wrapper(cwd):
           time_begin = time.ctime()
           print('Begin @' + time_begin)
           func(cwd)
           time_end = time.ctime()
           print('End @' + time_end)
   
           print('Begin @' + time_begin)
           print('End @' + time_end)
       return wrapper
   
   
   @timer
   def walk(cwd=r'D:\PyCharm\python\practice'):
       for root, dirs, files in os.walk(cwd):
           # print(root)  # 打印当前目录下的所有子目录的绝对路径
           # print(dirs)  # 打印每个目录下的子目录列表
           # print(files)  # 打印所有目录下文件列表
           print(root)
           for file in files:
               print('\t' + file)
   
   
   walk(cwd=r'D:\PyCharm')

4. 包含所有参数以及带返回值的装饰器

   # decorator_args.py  包含所有参数的装饰器
   import time
   def timer(func):
       def inner(*args, **kwargs):
           start = time.time()
           re = func(*args, **kwargs)
           end = time.time()
           return re
       return inner
   
   
   @timer  #==> func1 = timer(func1)
   def func1(a, b):
       print('in func1')
       return a, b
   
   
   @timer #==> func2 = timer(func2)
   def func2(a):
       print('In func2 and get', a)
       return 'func2 over'
   
   
   func1('aaaaaa', 'bbbbbb')
   print(func2('aaaaaa'))

5. 使被装饰的函数能够使用正常函数方法

   # decorator_method.py
   from functools import wraps
   
   def deco(func):
       @wraps(func)
       def wrapper(*args, **kwargs):
           return func(*args, **kwargs)
       return wrapper
   
   @deco
   def index():
       '''docs here in decorator'''
       print('from index')
   
   
   index()
   print(index.__name__)
   print(index.__doc__)