在没有 str 方法的情况下从类中检索数据 [英] Retrieving data from a class without the str method

问题描述

我拥有一个名为 Collat​​z 的类和一个创建类对象的函数 collat​​z_it，我正在尝试生成一个数字要达到的步骤数1 使用 collat​​z conjucture 及其相应的步骤，直到 100 万使用生成器

I posses a class called Collatz and a function collatz_it which creates an object of the class, I'm trying to generate the number of steps for a number to reach 1 using the collatz conjucture and their corresponding steps till 1 million using a generator

import collatz
values = {}
count = 0
#collatz.collatz_it(n)

def gen():
    n = 0
    x = 0
    while True:
        yield x
        n += 1
        x = collatz.collatz_it(n)

for i in gen():
    count += 1
    values[count] = i
    print values
    if count == 1000000:
        break

如您所见，我使用collat​​z猜想为给定的数字生成达到1所需的步数，并将其添加到具有相应数字的字典中但是当我打印出来时字典值，它的输出很尴尬:

As you can see, I generate the amount of steps taken for it to reach 1 using the collatz conjecture for a number given and add it to a dictionary with the corresponding number but when I print out the dictionary values, it's output is awkwardly something like this:

{1: 0}
{1: 0, 2: <collatz.Collatz instance at 0x01DCA580>}
{1: 0, 2: <collatz.Collatz instance at 0x01DCA580>, 3: <collatz.Collatz instance at 0x01DCDF58>}
{1: 0, 2: <collatz.Collatz instance at 0x01DCA580>, 3: <collatz.Collatz instance at 0x01DCDF58>, 4: <collatz.Collatz instance at 0x01DCDFA8>}
{1: 0, 2: <collatz.Collatz instance at 0x01DCA580>, 3: <collatz.Collatz instance at 0x01DCDF58>, 4: <collatz.Collatz instance at 0x01DCDFA8>, 5: <collatz.Collatz instance at 0x01DCDEB8>}
{1: 0, 2: <collatz.Collatz instance at 0x01DCA580>, 3: <collatz.Collatz instance at 0x01DCDF58>, 4: <collatz.Collatz instance at 0x01DCDFA8>, 5: <collatz.Collatz instance at 0x01DCDEB8>, 6: <collatz.Collatz instance at 0x01DCDE90>}
{1: 0, 2: <collatz.Collatz instance at 0x01DCA580>, 3: <collatz.Collatz instance at 0x01DCDF58>, 4: <collatz.Collatz instance at 0x01DCDFA8>, 5: <collatz.Collatz instance at 0x01DCDEB8>, 6: <collatz.Collatz instance at 0x01DCDE90>, 7: <collatz.Collatz instance at 0x01DE8940>}

如果我打印 print i 而不是 print values 我得到所需的输出，这基本上是因为 print 语句触发了 __str__ 类中的方法

If I print print i instead of print values I get the required output, this is basically because the print statement triggers the __str__ method in the class

是否有任何方法可以在不输入 <collat​​z.Collat​​z 实例 at 0x01DCDFA8> 的情况下将实际步骤添加到字典中，是否有任何方法可以从 <collat​​z.Collat​​z 实例中检索数据?code>__str__ 方法使我的字典看起来像这样:

Isn't there any way I could add the actual steps to the dictionary without entering <collatz.Collatz instance at 0x01DCDFA8> , Is there any sort of method of retrieving data as from a __str__ method so that my dictionary looks something like this:

{1: 0}
{1: 0, 2: 1}
{1: 0, 2: 1, 3: 7}

推荐答案

任何 Python 容器的默认表示是使用内容的 repr() 输出，而不是 str().

The default representation of any Python container is to use the repr() output of the contents, not str().

解决方案是给 collat​​z.Collat​​z() 实例一个 __repr__ 方法(你可以用猴子补丁)，或者使用一个dict 的子类，在显示内容时使用 str() 而不是 repr().

The solution would be for you to either give the collatz.Collatz() instance a __repr__ method (you can monkey-patch that in), or to use a subclass of dict that uses str() instead of repr() when displaying the contents.

__repr__ 中的猴子补丁可以很简单:

Monkey-patching in a __repr__ could be as simple as:

collatz.Collatz.__repr__ = collatz.Collatz.__str__

当然，如果这是您自己的代码，只需在类主体中定义一个__repr__方法即可.

Of course, if this is your own code, just define a __repr__ method in the class body itself.

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