总结Python中装饰器的使用介绍

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>>> @make_bold
... def get_content():
...  return 'hello world'
...
>>> get_content()
'<b>hello world</b>' 

def get_content():
  return 'hello world' 

>>> id(get_content)
140090200473112
>>> type(get_content)
<class 'function'>
>>> get_content
<function get_content at 0x7f694aa2be18> 

>>> func_name = get_content
>>> func_name()
'hello world' 

>>> def foo(bar):
...   print(bar())
...   return bar
...
>>> func = foo(get_content)
hello world
>>> func()
'hello world' 

class FuncObj(object):
  def init(self, name):
    print('Initialize')
    self.name= name

  def call(self):
    print('Hi', self.name) 

>>> fo = FuncObj('python')
Initialize
>>> fo()
Hi python 

@make_bold
def get_content():
  return 'hello world'

# 上面的代码等价于下面的

def get_content():
  return 'hello world'
get_content = make_bold(get_content) 

class make_bold(object):
  def init(self, func):
    print('Initialize')
    self.func = func

  def call(self):
    print('Call')
    return '<b>{}</b>'.format(self.func()) 

>>> @make_bold
... def get_content():
...   return 'hello world'
...
Initialize
>>> get_content()
Call
'<b>hello world</b>' 

>>> get_content = make_bold(get_content)
Initialize

# 调用，实际上直接调用的是make_bold构造出来的函数对象
>>> get_content()
Call
'<b>hello world</b>' 

>>> globals()
{}
>>> def func():
...   pass
...
>>> globals()
{'func': <function func at 0x10f5baf28>} 

class NoName(object):
  def call(self):
    pass

func = NoName() 

def outer():
  print('Before def:', locals())
  def inner():
    pass
  print('After def:', locals())
  return inner 

>>> outer()
Before def: {}
After def: {'inner': <function outer.<locals>.inner at 0x7f0b18fa0048>}
<function outer.<locals>.inner at 0x7f0b18fa0048>
>>> outer()
Before def: {}
After def: {'inner': <function outer.<locals>.inner at 0x7f0b18fa00d0>}
<function outer.<locals>.inner at 0x7f0b18fa00d0> 

def outer():
  msg = 'hello world'
  def inner():
    print(msg)
  return inner 

>>> func = outer()
>>> func()
hello world 

def make_bold(func):
  print('Initialize')
  def wrapper():
    print('Call')
    return '<b>{}</b>'.format(func())
  return wrapper 

>>> @make_bold
... def get_content():
...   return 'hello world'
...
Initialize
>>> get_content()
Call
'<b>hello world</b>' 

>>> @make_header(2)
... def get_content():
...   return 'hello world'
...
>>> get_content()
'<h2>hello world</h2>' 

@make_header(2)
def get_content():
  return 'hello world'

# 等价于

def get_content():
  return 'hello world'
unnamed_decorator = make_header(2)
get_content = unnamed_decorator(get_content) 

def make_header(level):
  print('Create decorator')

  # 这部分跟通常的装饰器一样，只是wrapper通过闭包访问了变量level
  def decorator(func):
    print('Initialize')
    def wrapper():
      print('Call')
      return '<h{0}>{1}</h{0}>'.format(level, func())
    return wrapper

  # make_header返回装饰器
  return decorator 

>>> @make_header(2)
... def get_content():
...   return 'hello world'
...
Create decorator
Initialize
>>> get_content()
Call
'<h2>hello world</h2>' 

@make_bold
def get_login_tip(name):
  return 'Welcome back, {}'.format(name) 

class make_bold(object):
  def init(self, func):
    self.func = func

  def call(self, name):
    return '<b>{}</b>'.format(self.func(name)) 

class make_bold(object):
  def init(self, func):
    self.func = func
  def call(self, *args, **kwargs):
    return '<b>{}</b>'.format(self.func(*args, **kwargs)) 

@make_italic
@make_bold
def get_content():
  return 'hello world' 

def get_content():
  return 'hello world'
get_content = make_bold(get_content) # 先装饰离函数定义近的
get_content = make_italic(get_content) 

import functools

def make_bold(func):
  @functools.wraps(func)
  def wrapper(*args, **kwargs):
    return '<b>{}</b>'.format(func(*args, **kwargs))
  return wrapper 

>>> @make_bold
... def get_content():
...   '''Return page content'''
...   return 'hello world'

# 不用functools.wraps的结果
>>> get_content.name
'wrapper'
>>> get_content.doc
>>>

# 用functools.wraps的结果
>>> get_content.name
'get_content'
>>> get_content.doc
'Return page content' 

实现装饰器时往往不知道调用方会怎么用，所以养成好习惯加上 functools.wraps 吧。

这次是真·完结了，撒花吧~~~

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