编写将装饰器应用于所有方法的类装饰器 [英] Writing a class decorator that applies a decorator to all methods

问题描述

我正在尝试编写一个将装饰器应用于所有类方法的类装饰器：

I'm trying to write a class decorator that applies a decorator to all the class' methods:

import inspect


def decorate_func(func):
    def wrapper(*args, **kwargs):
        print "before"
        ret = func(*args, **kwargs)
        print "after"
        return ret
    for attr in "__module__", "__name__", "__doc__":
        setattr(wrapper, attr, getattr(func, attr))
    return wrapper


def decorate_class(cls):
    for name, meth in inspect.getmembers(cls, inspect.ismethod):
        setattr(cls, name, decorate_func(meth))
    return cls


@decorate_class
class MyClass(object):

    def __init__(self):
        self.a = 10
        print "__init__"

    def foo(self):
        print self.a

    @staticmethod
    def baz():
        print "baz"

    @classmethod
    def bar(cls):
        print "bar"


obj = MyClass()
obj.foo()
obj.baz()
MyClass.baz()
obj.bar()
MyClass.bar()

这几乎可行，但是 @classmethod S需要特殊处理：

It almost works, but @classmethodS need a special treatment:

$ python test.py
before
__init__
after
before
10
after
baz
baz
before
Traceback (most recent call last):
  File "test.py", line 44, in <module>
    obj.bar()
  File "test.py", line 7, in wrapper
    ret = func(*args, **kwargs)
TypeError: bar() takes exactly 1 argument (2 given)

有没有一种方法可以很好地处理此问题？我检查了 @classmethod 装饰的方法，但看不到任何可将它们与其他类型方法区分开的东西。

Is there a way to handle this problem nicely ? I inspected @classmethod decorated methods, but I don't see anything to differentiate them from other "types" of methods.

更新

这是记录的完整解决方案（使用描述符处理 @staticmethod S和 @classmethod S很好，以及aix的技巧来检测 @classmethod S VS普通方法）：

Here is the complete solution for the record (using descriptors to handle @staticmethodS and @classmethodS nicely, and aix's trick to detect @classmethodS VS normal methods):

import inspect


class DecoratedMethod(object):

    def __init__(self, func):
        self.func = func

    def __get__(self, obj, cls=None):
        def wrapper(*args, **kwargs):
            print "before"
            ret = self.func(obj, *args, **kwargs)
            print "after"
            return ret
        for attr in "__module__", "__name__", "__doc__":
            setattr(wrapper, attr, getattr(self.func, attr))
        return wrapper


class DecoratedClassMethod(object):

    def __init__(self, func):
        self.func = func

    def __get__(self, obj, cls=None):
        def wrapper(*args, **kwargs):
            print "before"
            ret = self.func(*args, **kwargs)
            print "after"
            return ret
        for attr in "__module__", "__name__", "__doc__":
            setattr(wrapper, attr, getattr(self.func, attr))
        return wrapper


def decorate_class(cls):
    for name, meth in inspect.getmembers(cls):
        if inspect.ismethod(meth):
            if inspect.isclass(meth.im_self):
                # meth is a classmethod
                setattr(cls, name, DecoratedClassMethod(meth))
            else:
                # meth is a regular method
                setattr(cls, name, DecoratedMethod(meth))
        elif inspect.isfunction(meth):
            # meth is a staticmethod
            setattr(cls, name, DecoratedClassMethod(meth))
    return cls


@decorate_class
class MyClass(object):

    def __init__(self):
        self.a = 10
        print "__init__"

    def foo(self):
        print self.a

    @staticmethod
    def baz():
        print "baz"

    @classmethod
    def bar(cls):
        print "bar"


obj = MyClass()
obj.foo()
obj.baz()
MyClass.baz()
obj.bar()
MyClass.bar()

推荐答案

inspect.isclass（meth.im_self）应该告诉您 meth 是否是一个类方法：

inspect.isclass(meth.im_self) should tell you whether meth is a class method:

def decorate_class(cls):
    for name, meth in inspect.getmembers(cls, inspect.ismethod):
        if inspect.isclass(meth.im_self):
          print '%s is a class method' % name
          # TODO
        ...
    return cls

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