Question

我正在使用MIT OCW，并且刚刚学习了有关类的知识。因此，当在一对实例上调用相等方法时，我的代码（从原始代码中编辑）一次又一次地调用自身。代码如下：

class Animal(object):
def __init__(self, age):
    self.age = age
    self.name = None
def __str__(self):
    return "animal:"+str(self.name)+":"+str(self.age)


class Rabbit(Animal):
    tag = 1
    def __init__(self, age, parent1=None, parent2=None):
        Animal.__init__(self, age)
        self.parent1 = parent1
        self.parent2 = parent2
        self.rid = Rabbit.tag
        Rabbit.tag += 1
    def __eq__(self, other):
        print('entering equality')
        print(self.parent1)
        print(self.parent2)
        parents_same = self.parent1== other.parent1 and self.parent2== other.parent2
        print('1st comp')
        parents_opposite = self.parent2 == other.parent1 and self.parent1== other.parent2
        print('2nd comp')
        return parents_same or parents_opposite

a=Rabbit(6)
b=Rabbit(7)
c=Rabbit(5,a,b)
d=Rabbit(3,a,b)
e=Rabbit(2,c,d)
f=Rabbit(1,c,d)

print(e==f)

运行此代码后，可以看到Python多次进入相等循环。以下是原始的 eq 属性：

def __eq__(self, other):
    parents_same = self.parent1.rid == other.parent1.rid \
    and self.parent2.rid == other.parent2.rid
    parents_opposite = self.parent2.rid == other.parent1.rid \
    and self.parent1.rid == other.parent2.rid
    return parents_same or parents_opposite

使用原始的equals属性，代码可以正常运行。谁能解释我为什么会这样。谢谢。

Answer 1

因为您要检查多只兔子的相等性！ { // Use IntelliSense to learn about possible attributes. // Hover to view descriptions of existing attributes. // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387 "version": "0.2.0", "configurations": [ { "name": "Python: Current File (Integrated Terminal)", "type": "python", "request": "launch", "program": "${file}", "console": "integratedTerminal" }, { "name": "Python: Remote Attach", "type": "python", "request": "attach", "port": 5678, "host": "localhost", "pathMappings": [ { "localRoot": "${workspaceFolder}", "remoteRoot": "." } ] }, { "name": "Python: Module", "type": "python", "request": "launch", "module": "enter-your-module-name-here", "console": "integratedTerminal" }, { "name": "Python: Django", "type": "python", "request": "launch", "program": "${workspaceFolder}/IA_TD2.py", "console": "integratedTerminal", "args": [ "runserver", "--noreload", "--nothreading" ], "django": true }, { "name": "Python: Flask", "type": "python", "request": "launch", "module": "flask", "env": { "FLASK_APP": "app.py" }, "args": [ "run", "--no-debugger", "--no-reload" ], "jinja": true }, { "name": "Python: Current File (External Terminal)", "type": "python", "request": "launch", "program": "${file}", "console": "externalTerminal" }, { "name": "Python: Current File (None)", "type": "python", "request": "launch", "program": "${file}", "console": "none" } ]对象的父母也是兔子，每个对象都有父母的兔子。因此，每次相等检查将递归调用e, f，直到您到达Rabbit.__eq__和a

为什么一类的平等属性一遍又一遍地调用自己？

1 个答案: