【參考】:http://python.jobbole.com/81683/
【參考】:https://www.cnblogs.com/lianyingteng/p/7743876.html
1、閉包函數:
如果內部函數裏引用了外部函數裏定義的變量,那麼此時內部函數就稱爲閉包函數。閉包函數所引用的外部定義變量(非全局變量)叫做自用變量。閉包可以將自己的代碼和作用域以及外部函數結合使用。
def count():
a, b = 1, 1
def sum():
c = 1
return a + b + c
return sum
2、裝飾器:
python裝飾器本質上就是一個函數,它可以讓其他函數在不需要做任何代碼變動的前提下增加額外的功能,裝飾器的返回值也就是,必須是一個函數的對象。裝飾器函數的外部函數傳入我要裝飾的函數名字,返回經過修改後的函數名字;內部函數(閉包)負責修飾裝飾函數:
- 實質:一個函數;
- 參數:是你要裝飾的函數名(並非函數調用,[缺少()])
- 返回:是裝飾完的函數名(非函數調用)
- 作用:爲已經存在對象添加額外的功能;
- 特點:不需要對對象做任何的代碼上的改動
{裝飾器的最大作用,定義一些基本的功能,然後再需要調用借本功能的函數前使用}
class Coordinate: def __init__(self, x, y): self.x = x self.y = y def __repr__(self): return "Coord:" + str(self.__dict__) 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 @wrapper def add(a, b): return Coordinate(a.x + b.x, a.y + b.y) @wrapper def sub(a, b): return Coordinate(a.x - b.x, a.y - b.y) if __name__ == "__main__": coor_a = Coordinate(-100, 200) coor_b = Coordinate(100, -200) print(add(coor_a,coor_b))
3、類裝飾器:
類似於函數裝飾器,只不過應用場景是類,用於管理類自身或攔截類實例創建等;
# --coding='utf-8'-- #單實例管理 instances = {} def getInstance(aClass, *args): if aClass not in instances: instances[aClass] = aClass(*args) return instances[aClass] def singleton(aClass): def onCall(*args): return getInstance(aClass, *args) return onCall @singleton class Person: def __init__(self, name, hours, rate): self.name = name self.hours = hours self.rate = rate def pay(self): return self.hours * self.rate @singleton class Spam: def __init__(self, val): self.attr = val if __name__ == "__main__": bob = Person('Bob', 40, 10) print(bob.name, bob.pay()) sue = Person('sue', 50, 20) print(sue.name, sue.pay()) X = Spam(42) Y = Spam(22) print(X.attr, Y.attr)
# -- coding:utf-8 -- #跟蹤對象接口 def Tracer(aClass): class Wrapper: def __init__(self, *args, **kargs): self.fetchers = 0 self.wrapped = aClass(*args, **kargs) def __getattr__(self, attrname): print('Trace:' + attrname) self.fetchers += 1 return getattr(self.wrapped, attrname) return Wrapper @Tracer class Spam: def display(self): print('spam' * 8) @Tracer class Person: def __init__(self, name, hours, rate): self.name = name self.hours = hours self.rate = rate def pay(self): return self.hours * self.rate if __name__ == "__main__": food = Spam() food.display() print(food.fetchers) bob = Person('Bob', 12, 22) print(bob.name, bob.pay()) sue = Person('Sue', 10, 27) print(sue.name) print(bob.fetchers) print(sue.fetchers)