[英]Writing a class decorator that applies a decorator to all methods
我正在尝试编写一个 class 装饰器,它将装饰器应用于所有类的方法:
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()
它几乎可以工作,但@classmethod
S 需要特殊处理:
$ 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)
有没有办法很好地处理这个问题? 我检查@classmethod
修饰的方法,但我没有看到任何可以将它们与其他“类型”方法区分开来的东西。
更新
这是记录的完整解决方案(使用描述符很好地处理@staticmethod
S和@classmethod
S,以及aix检测@classmethod
S VS普通方法的技巧):
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()
inspect.isclass(meth.im_self)
应该告诉你meth
是否是 class 方法:
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
(评论太长了)
我冒昧地添加了指定哪些方法应该被装饰到您的解决方案的能力:
def class_decorator(*method_names):
def wrapper(cls):
for name, meth in inspect.getmembers(cls):
if name in method_names or len(method_names) == 0:
if inspect.ismethod(meth):
if inspect.isclass(meth.im_self):
# meth is a classmethod
setattr(cls, name, VerifyTokenMethod(meth))
else:
# meth is a regular method
setattr(cls, name, VerifyTokenMethod(meth))
elif inspect.isfunction(meth):
# meth is a staticmethod
setattr(cls, name, VerifyTokenMethod(meth))
return cls
return wrapper
用法:
@class_decorator('some_method')
class Foo(object):
def some_method(self):
print 'I am decorated'
def another_method(self):
print 'I am NOT decorated'
以上答案并不直接适用于 python3。 基于其他很好的答案,我已经能够提出以下解决方案:
import inspect
import types
import networkx as nx
def override_methods(cls):
for name, meth in inspect.getmembers(cls):
if name in cls.methods_to_override:
setattr(cls, name, cls.DecorateMethod(meth))
return cls
@override_methods
class DiGraph(nx.DiGraph):
methods_to_override = ("add_node", "remove_edge", "add_edge")
class DecorateMethod:
def __init__(self, func):
self.func = func
def __get__(self, obj, cls=None):
def wrapper(*args, **kwargs):
ret = self.func(obj, *args, **kwargs)
obj._dirty = True # This is the attribute I want to update
return ret
return wrapper
def __init__(self):
super().__init__()
self._dirty = True
现在,只要调用元组methods_to_override
中的方法,就会设置脏标志。 当然,其他任何东西也可以放在那里。 没有必要在需要覆盖其方法的 class 中包含DecorateMethod
class。 但是,由于DecorateMehod
使用 class 的特定属性,我更喜欢创建 class 属性。
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