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
在你的类中实现__eq__方法;就像这样:
def __eq__(self, other):
return self.path == other.path and self.title == other.title
编辑:如果你想让你的对象比较相等当且仅当它们有相等的实例字典:
def __eq__(self, other):
return self.__dict__ == other.__dict__
其他回答
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)
在你的类中实现__eq__方法;就像这样:
def __eq__(self, other):
return self.path == other.path and self.title == other.title
编辑:如果你想让你的对象比较相等当且仅当它们有相等的实例字典:
def __eq__(self, other):
return self.__dict__ == other.__dict__
你应该实现方法__eq__:
class MyClass:
def __init__(self, foo, bar, name):
self.foo = foo
self.bar = bar
self.name = name
def __eq__(self,other):
if not isinstance(other,MyClass):
return NotImplemented
else:
#string lists of all method names and properties of each of these objects
prop_names1 = list(self.__dict__)
prop_names2 = list(other.__dict__)
n = len(prop_names1) #number of properties
for i in range(n):
if getattr(self,prop_names1[i]) != getattr(other,prop_names2[i]):
return False
return True
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。
我写了这个，并把它放在我的项目中的test/utils模块中。对于情况下，当它不是一个类，只是计划ol' dict，这将遍历两个对象，并确保
每个属性都与其对应的属性相等 不存在悬空属性(只存在于一个对象上的attrs)
它的大…这一点都不性感……但是，哦，boi，它工作!
def assertObjectsEqual(obj_a, obj_b):
def _assert(a, b):
if a == b:
return
raise AssertionError(f'{a} !== {b} inside assertObjectsEqual')
def _check(a, b):
if a is None or b is None:
_assert(a, b)
for k,v in a.items():
if isinstance(v, dict):
assertObjectsEqual(v, b[k])
else:
_assert(v, b[k])
# Asserting both directions is more work
# but it ensures no dangling values on
# on either object
_check(obj_a, obj_b)
_check(obj_b, obj_a)
您可以通过删除_assert并使用普通的ol' assert来稍微清理它，但当它失败时，您得到的消息是非常没有帮助的。
