我有一个类MyClass，它包含两个成员变量foo和bar:
class MyClass:
def __init__(self, foo, bar):
self.foo = foo
self.bar = bar
我有这个类的两个实例，每个实例都有相同的foo和bar值:
x = MyClass('foo', 'bar')
y = MyClass('foo', 'bar')
然而，当我比较它们是否相等时，Python返回False:
>>> x == y
False
我如何使python认为这两个对象相等?
当前回答
下面通过在两个对象层次结构之间进行深度比较来工作(在我有限的测试中)。In处理各种情况，包括对象本身或其属性是字典的情况。
def deep_comp(o1:Any, o2:Any)->bool:
# NOTE: dict don't have __dict__
o1d = getattr(o1, '__dict__', None)
o2d = getattr(o2, '__dict__', None)
# if both are objects
if o1d is not None and o2d is not None:
# we will compare their dictionaries
o1, o2 = o1.__dict__, o2.__dict__
if o1 is not None and o2 is not None:
# if both are dictionaries, we will compare each key
if isinstance(o1, dict) and isinstance(o2, dict):
for k in set().union(o1.keys() ,o2.keys()):
if k in o1 and k in o2:
if not deep_comp(o1[k], o2[k]):
return False
else:
return False # some key missing
return True
# mismatched object types or both are scalers, or one or both None
return o1 == o2
这是一个非常棘手的代码，所以请在注释中添加任何可能不适合你的情况。
其他回答
根据具体情况，你可以这样做:
>>> vars(x) == vars(y)
True
参见对象字段中的Python字典
我尝试了最初的示例(参见上面的7)，它在ipython中不起作用。注意，cmp(obj1,obj2)在使用两个相同的对象实例实现时返回“1”。奇怪的是，当我修改其中一个属性值并重新比较时，使用cmp(obj1,obj2)对象继续返回“1”。(叹息…)
好的，所以你需要做的是迭代两个对象，并使用==号比较每个属性。
如果你想逐个属性进行比较，并查看它是否以及在哪里失败，你可以使用下面的列表推导式:
[i for i,j in
zip([getattr(obj_1, attr) for attr in dir(obj_1)],
[getattr(obj_2, attr) for attr in dir(obj_2)])
if not i==j]
这里的额外优势是，当在PyCharm中调试时，您可以压缩一行并在“Evaluate Expression”窗口中输入。
总结如下:
It's advised to implement __eq__ rather than __cmp__, except if you run python <= 2.0 (__eq__ has been added in 2.1) Don't forget to also implement __ne__ (should be something like return not self.__eq__(other) or return not self == other except very special case) Don`t forget that the operator must be implemented in each custom class you want to compare (see example below). If you want to compare with object that can be None, you must implement it. The interpreter cannot guess it ... (see example below) class B(object): def __init__(self): self.name = "toto" def __eq__(self, other): if other is None: return False return self.name == other.name class A(object): def __init__(self): self.toto = "titi" self.b_inst = B() def __eq__(self, other): if other is None: return False return (self.toto, self.b_inst) == (other.toto, other.b_inst)
重写对象中的富比较运算符。
class MyClass:
def __lt__(self, other):
# return comparison
def __le__(self, other):
# return comparison
def __eq__(self, other):
# return comparison
def __ne__(self, other):
# return comparison
def __gt__(self, other):
# return comparison
def __ge__(self, other):
# return comparison
是这样的:
def __eq__(self, other):
return self._id == other._id
