多个装饰器执行顺序

多个装饰器的执行顺序

def decorator_a(func):
    print 'Get in decorator_a'
    def inner_a(*args, **kwargs):
        print 'Get in inner_a'
        return func(*args, **kwargs)
    return inner_a

def decorator_b(func):
    print 'Get in decorator_b'
    def inner_b(*args, **kwargs):
        print 'Get in inner_b'
        return func(*args, **kwargs)
    return inner_b

@decorator_b#f=decorator_b(f)
@decorator_a#f=decorator_a(f)
def f(x):
    print 'Get in f'
    return x * 2

"""

Get in decorator_a
Get in decorator_b

"""

等同于

def decorator_a(func):
    print('Get in decorator_a')
    def inner_a(*args, **kwargs):
        print('Get in inner_a')
        return func(*args, **kwargs)
    return inner_a

def decorator_b(func):
    print('Get in decorator_b')
    def inner_b(*args, **kwargs):
        print('Get in inner_b')
        return func(*args, **kwargs)
    return inner_b

def f(x):
    print('Get in f')
    return x * 2


f=decorator_a(f)
f=decorator_b(f)




"""

Get in decorator_a
Get in decorator_b

"""

得出结论 装饰器函数在被装饰函数定义好后立即执行 并且是从下往上执行，最后的两句代码等同于

f=decorator_b(decorator_a(f))，执行顺序是从里到外，最先调用最里层的装饰器，最后调用最外层的装饰器

def decorator_a(func):
    print('Get in decorator_a')
    def inner_a(*args, **kwargs):
        print('Get in inner_a')
        return func(*args, **kwargs)
    return inner_a

def decorator_b(func):
    print('Get in decorator_b')
    def inner_b(*args, **kwargs):
        print('Get in inner_b')
        return func(*args, **kwargs)
    return inner_b

@decorator_b#f=decorator_b(f)
@decorator_a#f=decorator_a(f)
def f(x):
    print('Get in f')
    return x * 2
f(1)
"""

Get in decorator_a
Get in decorator_b
Get in inner_b
Get in inner_a
Get in f

"""

当我们对f传入参数1进行调用时，inner_b被调用了，他会先打印Get in inner_b,然后在inner_b内部调用了inner_a,所以会再打印Get in inner_a,然后再inner_a内部调用原来的f,并且将结果作为最终的返回

总结：

装饰器函数在被装饰函数定义好后立即执行从下往上执行

函数调用时从上到下执行

实际应用过程中，先验证有没有登录，在验证权限够不够，采用从上到下的顺序来装饰函数

@login_required
@permision_allowed
def f()
  # Do something
  return