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