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如何检查python方法是否绑定？

2023-04-14 18:40:00

How do you check whether a python method is bound or not?

给定对方法的引用，是否有办法检查该方法是否绑定到对象？您还可以访问绑定到的实例吗？

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def isbound(method):
return method.im_self is not None

def instance(bounded_method):
return bounded_method.im_self

用户定义的方法：

When a user-defined method object is
created by retrieving a user-defined
function object from a class, its
im_self attribute is None and the
method object is said to be unbound.
When one is created by retrieving a
user-defined function object from a
class via one of its instances, its
im_self attribute is the instance, and
the method object is said to be bound.
In either case, the new method's
im_class attribute is the class from
which the retrieval takes place, and
its im_func attribute is the original
function object.

在Python 2.6和3.0中：

Instance method objects have new
attributes for the object and function
comprising the method; the new synonym
for im_self is __self__, and im_func
is also available as __func__. The old
names are still supported in Python
2.6, but are gone in 3.0.

在python 3中，__self__属性仅在绑定方法上设置。在普通函数(或未绑定方法，在python 3中只是普通函数)中，未将其设置为None。

使用这样的东西：

1 2	def is_bound(m): return hasattr(m, '__self__')

所选答案几乎在所有情况下均有效。但是，当使用选择的答案检查方法是否绑定到装饰器中时，检查将失败。考虑以下示例装饰器和方法：

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def my_decorator(*decorator_args, **decorator_kwargs):
def decorate(f):
print(hasattr(f, '__self__'))
@wraps(f)
def wrap(*args, **kwargs):
return f(*args, **kwargs)
return wrap
return decorate

class test_class(object):
@my_decorator()
def test_method(self, *some_params):
pass

装饰器中的print语句将打印False。
在这种情况下，除了使用函数的参数名称检查函数参数并寻找一个名为self的方法外，我找不到其他方法。这也不保证可以正常工作，因为方法的第一个参数不必强制命名为self并且可以具有任何其他名称。

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