检查类属性是否有 setter [英] Check if class property has a setter

问题描述

我需要列出一个类的所有属性，这些属性是属性并且有一个 setter.例如这个类:

class MyClass(object):def __init__(self):自己.一 = 1self._b = 2self._c = 3@财产定义 b(自我):返回 self._b@财产def c(self):返回 [e-mail] c(self, value):self._c = 值

我需要获取属性 c 而不是 a 和 b.使用此答案:https://stackoverflow.com/a/5876258/7529716我可以得到属性对象 b 和 c.

但这是他们知道这些属性是否有除尝试之外的 setter 的一种方式:

inst = MyClass()尝试:上一个 = inst.binst.b = 无除了属性错误:pass # 没有 setter最后:inst.b = 上一个

提前致谢.

解决方案

property 对象 将它们的getter、setter 和deleter 分别存储在fget、fset 和fdel 属性中.如果属性没有设置器或删除器，则该属性设置为 None.

这意味着您可以简单地过滤掉那些 fset 属性设置为 None 的属性:

def get_writeable_properties(cls):返回 [attr 的属性，vars(cls).items() 中的值如果 isinstance(value, property) 和 value.fset 不是 None]

<预><代码>>>>get_writeable_properties(MyClass)['C']

I need to list all the attribute of a class that are properties and have a setter. For example with this class:

class MyClass(object):
    def __init__(self):
        self. a = 1
        self._b = 2
        self._c = 3

    @property
    def b(self):
        return self._b

    @property
    def c(self):
        return self._c

    @c.setter
    def c(self, value):
        self._c = value

I need to get the attribute c but not a and b. Using this answers: https://stackoverflow.com/a/5876258/7529716 i can get the property object b and c.

But is their a way to know if those properties have a setter other than trying:

inst = MyClass()    
try:
    prev = inst.b
    inst.b = None
except AttributeError:
    pass # No setter
finally:
    inst.b = prev  

Thanks in advance.

解决方案

property objects store their getter, setter and deleter in the fget, fset and fdel attributes, respectively. If a property doesn't have a setter or deleter, the attribute is set to None.

This means you can simply filter out those properties whose fset attribute is set to None:

def get_writeable_properties(cls):
    return [attr for attr, value in vars(cls).items()
                 if isinstance(value, property) and value.fset is not None]

>>> get_writeable_properties(MyClass)
['c']

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