python デコレータ

いい例があった。

def outer(some_func):
  def inner():
    print( "before some_func" )
    ret = some_func() #1
    return ret + 1
  return inner

def foo():
  return 1

decorated = outer(foo) #2
decorated()
#before some_func
#2

class Coordinate(object):
  def __init__(self, x, y):
    self.x = x
    self.y = y
  def __repr__(self):
    return "Coord: " + str(self.__dict__)

def add(a, b):
    return Coordinate(a.x + b.x, a.y + b.y)

def sub(a, b):
    return Coordinate(a.x - b.x, a.y - b.y)

def wrapper(func):
  def checker(a, b):
    if a.x < 0 or a.y < 0:
      a = Coordinate(a.x if a.x > 0 else 0, a.y if a.y > 0 else 0)
    if b.x < 0 or b.y < 0:
      b = Coordinate(b.x if b.x > 0 else 0, b.y if b.y > 0 else 0) 
    ret = func(a, b)
    if ret.x < 0 or ret.y < 0:
      ret = Coordinate(ret.x if ret.x > 0 else 0, ret.y if ret.y > 0 else 0)
    return ret
  return checker

add = wrapper(add)
sub = wrapper(sub)
one = Coordinate(100, 200)
two = Coordinate(300, 200)
three = Coordinate(-100, -100)
add(one, two)
# Coord: {'y': 400, 'x': 400}
sub(one, two)
#Coord: {'y': 0, 'x': -200}
add(one, three)
#Coord: {'y': 100, 'x': 0}

def logger(func):

     def inner(*args, **kwargs): #1

         print( "Arguments were: %s, %s" % (args, kwargs))

         return func(*args, **kwargs) #2

     return inner