类的Python functools.wraps等效项
类的Python functools.wraps等效项
提问于 2011-06-18 15:20:10
使用类定义装饰器时，如何在__name__、__module__和__doc__上自动传输？通常，我会使用functools中的@wraps装饰器。下面是我为一个类所做的事情(这并不完全是我的代码)：
class memoized:
"""Decorator that caches a function's return value each time it is called.
If called later with the same arguments, the cached value is returned, and
not re-evaluated.
"""
def __init__(self, func):
super().__init__()
self.func = func
self.cache = {}
def __call__(self, *args):
try:
return self.cache[args]
except KeyError:
value = self.func(*args)
self.cache[args] = value
return value
except TypeError:
# uncacheable -- for instance, passing a list as an argument.
# Better to not cache than to blow up entirely.
return self.func(*args)
def __repr__(self):
return self.func.__repr__()
def __get__(self, obj, objtype):
return functools.partial(self.__call__, obj)
__doc__ = property(lambda self:self.func.__doc__)
__module__ = property(lambda self:self.func.__module__)
__name__ = property(lambda self:self.func.__name__)有没有一个标准的装饰器可以自动创建name、module和doc？另外，为了自动化get方法(我假设这是用于创建绑定方法？)是否有遗漏的方法？
回答 5
Stack Overflow用户
回答已采纳
发布于 2013-07-18 00:36:16
每个人似乎都错过了显而易见的解决方案。
>>> import functools
>>> class memoized(object):
"""Decorator that caches a function's return value each time it is called.
If called later with the same arguments, the cached value is returned, and
not re-evaluated.
"""
def __init__(self, func):
self.func = func
self.cache = {}
functools.update_wrapper(self, func) ## TA-DA! ##
def __call__(self, *args):
pass # Not needed for this demo.
>>> @memoized
def fibonacci(n):
"""fibonacci docstring"""
pass # Not needed for this demo.
>>> fibonacci
<__main__.memoized object at 0x0156DE30>
>>> fibonacci.__name__
'fibonacci'
>>> fibonacci.__doc__
'fibonacci docstring'Stack Overflow用户
发布于 2020-12-28 05:02:59
事实证明，使用functools.wraps本身有一个简单的解决方案：
import functools
def dec(cls):
@functools.wraps(cls, updated=())
class D(cls):
decorated = 1
return D
@dec
class C:
"""doc"""
print(f'{C.__name__=} {C.__doc__=} {C.__wrapped__=}')$ python3 t.py
C.__name__='C' C.__doc__='doc' C.__wrapped__=<class '__main__.C'>请注意，需要使用updated=()来防止尝试更新类的__dict__ (此输出没有updated=())：
$ python t.py
Traceback (most recent call last):
File "t.py", line 26, in <module>
class C:
File "t.py", line 20, in dec
class D(cls):
File "/usr/lib/python3.8/functools.py", line 57, in update_wrapper
getattr(wrapper, attr).update(getattr(wrapped, attr, {}))
AttributeError: 'mappingproxy' object has no attribute 'update'Stack Overflow用户
发布于 2016-12-22 10:50:14
我需要一些可以同时包装类和函数的东西，并编写了以下代码：
def wrap_is_timeout(base):
'''Adds `.is_timeout=True` attribute to objects returned by `base()`.
When `base` is class, it returns a subclass with same name and adds read-only property.
Otherwise, it returns a function that sets `.is_timeout` attribute on result of `base()` call.
Wrappers make best effort to be transparent.
'''
if inspect.isclass(base):
class wrapped(base):
is_timeout = property(lambda _: True)
for k in functools.WRAPPER_ASSIGNMENTS:
v = getattr(base, k, _MISSING)
if v is not _MISSING:
try:
setattr(wrapped, k, v)
except AttributeError:
pass
return wrapped
@functools.wraps(base)
def fun(*args, **kwargs):
ex = base(*args, **kwargs)
ex.is_timeout = True
return ex
return fun页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/6394511
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