Python中装饰器兼容加括号和不加括号的写法详解

@login_required
def my_view(request):
 ...
 return render(...)

@login_required(login_url='/accounts/login/')
def my_view(request):
 ...
 return render(...)

def doublewrap(f):
 '''
 a decorator decorator, allowing the decorator to be used as:
 @decorator(with, arguments, and=kwargs)
 or
 @decorator
 '''
 @wraps(f)
 def new_dec(*args, **kwargs):
  if len(args) == 1 and len(kwargs) == 0 and callable(args[0]):
   # actual decorated function
   return f(args[0])
  else:
   # decorator arguments
   return lambda realf: f(realf, *args, **kwargs)
 
 return new_dec

def test_doublewrap():
 from util import doublewrap
 from functools import wraps 
 
 @doublewrap
 def mult(f, factor=2):
  '''multiply a function's return value'''
  @wraps(f)
  def wrap(*args, **kwargs):
   return factor*f(*args,**kwargs)
  return wrap
 
 # try normal
 @mult
 def f(x, y):
  return x + y
 
 # try args
 @mult(3)
 def f2(x, y):
  return x*y
 
 # try kwargs
 @mult(factor=5)
 def f3(x, y):
  return x - y
 
 assert f(2,3) == 10
 assert f2(2,5) == 30
 assert f3(8,1) == 5*7

new_func = decorator(func)