>>> @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'