Python 装饰器 （十八）

装饰器是一个函数，用来包装别的函数的函数，并返回一个修改之后的函数对象，将其重新赋值原来的标识符，原始函数对象是无法访问的。

当执行该方法时：先执行装饰器内部的代码然后执行返回的对象。

装饰器原理

def decorate(func):
    print "start called func()!"
    func()
    
def func_1():
    print "This is func_1()"
    
decorate(func_1)

相当于

def decorate(func):
    print "start called func()!"
    return func
@decorate
def func_2():
    print "This is func_2()" 

func_2()

装饰的函数带有参数

def decorate(func):
    def _decorate(*agrs, **kwagrs):
        print "agrs:",agrs
        print "kwagrs",kwagrs
        func(*agrs, **kwagrs)
    return _decorate
    
@decorate
def func(*agrs, **kwagres):
    print "This is func()"
    
func(1,2,3,a=4,b=5,c=6)

装饰器带参数（需要再在外面包装一层函数）

def decorate(arg):
    if arg == 0:
        print "arg == 0"
        def _decorate_0(func):
            def __decorate_1(*agrs, **kwagrs):
                print "agrs:",agrs
                print "kwagrs",kwagrs
            return __decorate_1
        return _decorate_0
    elif arg == 1:
        print "arg == 1"
        def _adecorate_1(func):
            def __decorate_1(*agrs, **kwagrs):
                print "agrs:",agrs
                print "kwagrs",kwagrs
            return __decorate_1
        return _adecorate_1

@decorate(0)
def func_1(*agrs, **kwagres):
    print "This is func_1()"
    
@decorate(1)
def func_2(*agrs, **kwagres):
    print "This is func_1()"
    
func_1(1,2,3)
func_2(a=4,b=5,c=6)

内置的装饰器有三个，分别是staticmethod、classmethod和property，作用分别是把类中定义的实例方法变成静态方法、类方法和类属性。很少使用