[英]Writing a class decorator that applies a decorator to all methods
我正在嘗試編寫一個 class 裝飾器,它將裝飾器應用於所有類的方法:
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()
它幾乎可以工作,但@classmethod
S 需要特殊處理:
$ 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)
有沒有辦法很好地處理這個問題? 我檢查@classmethod
修飾的方法,但我沒有看到任何可以將它們與其他“類型”方法區分開來的東西。
更新
這是記錄的完整解決方案(使用描述符很好地處理@staticmethod
S和@classmethod
S,以及aix檢測@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)
應該告訴你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
(評論太長了)
我冒昧地添加了指定哪些方法應該被裝飾到您的解決方案的能力:
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'
以上答案並不直接適用於 python3。 基於其他很好的答案,我已經能夠提出以下解決方案:
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
現在,只要調用元組methods_to_override
中的方法,就會設置臟標志。 當然,其他任何東西也可以放在那里。 沒有必要在需要覆蓋其方法的 class 中包含DecorateMethod
class。 但是,由於DecorateMehod
使用 class 的特定屬性,我更喜歡創建 class 屬性。
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