Python通过装饰类动态给类的方法添加装饰器

Question

假设我有一个类:

class x:

    def first_x_method(self):
        print 'doing first_x_method stuff...'

    def second_x_method(self):
        print 'doing second_x_method stuff...'

和这个装饰器

class logger:
    @staticmethod
    def log(func):
        def wrapped(*args, **kwargs):
            try:
                print "Entering: [%s] with parameters %s" % (func.__name__, args)
                try:
                    return func(*args, **kwargs)
                except Exception, e:
                    print 'Exception in %s : %s' % (func.__name__, e)
            finally:
                print "Exiting: [%s]" % func.__name__
        return wrapped

我将如何编写另一个装饰器 otherdecorator 以便:

@otherdecorator(logger.log)
class x:

    def first_x_method(self):
        print 'doing x_method stuff...'

    def first_x_method(self):
        print 'doing x_method stuff...'

和

一样

class x:
      @logger.log
      def first_x_method(self):
          print 'doing first_x_method stuff...'

      @logger.log
      def second_x_method(self):
        print 'doing second_x_method stuff...'

或者实际上替换

@otherdecorator(logger.log)
class x:

与

@otherdecorator 
class x:

otherdecorator 包含所有功能(我不是 python 人所以要温柔)

Answer 1

除非有明确的理由使用类作为装饰器，否则我认为通常使用函数来定义装饰器更容易。

这是创建类装饰器 trace 的一种方法，它使用 log 装饰器装饰类的所有方法:

import inspect


def log(func):
    def wrapped(*args, **kwargs):
        try:
            print("Entering: [%s] with parameters %s" % (func.__name__, args))
            try:
                return func(*args, **kwargs)
            except Exception as e:
                print('Exception in %s : %s' % (func.__name__, e))
        finally:
            print("Exiting: [%s]" % func.__name__)
    return wrapped


def trace(cls):
    # https://stackoverflow.com/a/17019983/190597 (jamylak)
    for name, m in inspect.getmembers(cls, lambda x: inspect.isfunction(x) or inspect.ismethod(x)):
        setattr(cls, name, log(m))

    return cls


@trace
class X(object):
    def first_x_method(self):
        print('doing first_x_method stuff...')

    def second_x_method(self):
        print('doing second_x_method stuff...')


x = X()
x.first_x_method()
x.second_x_method()

产量:

Entering: [first_x_method] with parameters (<__main__.X object at 0x7f19e6ae2e80>,)
doing first_x_method stuff...
Exiting: [first_x_method]
Entering: [second_x_method] with parameters (<__main__.X object at 0x7f19e6ae2e80>,)
doing second_x_method stuff...
Exiting: [second_x_method]