Django：动态模型字段定义 [英] Django: Dynamic model field definition

问题描述

Hi Stackoverflow people，

Hi Stackoverflow people,

我有一个比较单调的模型定义，它包含1到50的bin的字段。

I have a model definition which is rather monotone, it includes fields for bins from 1 to 50.

为了概念证明，我用手写了它，但必须有一个更好的方法来自动化模型定义，并保持代码的整洁。

For the proof of concept, I wrote it by hand, but there must be a better way to automate the model definition and to keep the code nice and tidy.

到目前为止，我按照这样做：

So far I did it the follow way:

class Bins(models.Model):
    p1 = models.DecimalField(_('bin 1'), max_digits=6, decimal_places=2)
    p2 = models.DecimalField(_('bin 2'), max_digits=6, decimal_places=2)
    p3 = models.DecimalField(_('bin 3'), max_digits=6, decimal_places=2)
    ...
    p50 = ...

在 Django wiki ，我发现动态模型定义的摘要，但它似乎不允许在定义中的循环：

On the Django wiki, I found a summary for dynamic model definitions, but its seems that it does not allow for loops in the definition:

我已经尝试了下面的代码，但是我得到一个错误msg，MAX_BIN = 2是无效的语法。
我明白我不能像我所试过的那样迭代的错误。

I have tried the code below, but I get an error msg that MAX_BIN = 2 is an invalid syntax. I understand the error that I can't iterated over the field like I tried.

Bins = type('Bins', (models.Model,), {     
    MAX_BIN = 50
    for i in range(MAX_BIN):
        name_sects = ["p", str(i)]
        "".join(name_sects): model.DecimalField(_("".join([bin ', str(i)])),
                             max_digits=6, decimal_places=2)
    })

这样的动态类定义是否可以通用？
如果是，定义课程的最佳方法是什么？

感谢您的帮助！

推荐答案

在你当前的版本中，你的循环是在一个dict的定义内。这是不允许的。但是，您可以在调用类型之前的dict中定义您的字段，这样可以正常工作。像

in your current edition, your loop is inside the definition of a dict. that's not allowed. however, you could define your fields in a dict outside your call to type which works fine. something like

attrs = {
    other_field = models.IntegerField(),
    '__module__': 'myapp.models',
}

MAX_BIN = 50
   for i in range(MAX_BIN):
       name_sects = ["p", str(i)]
        attrs["".join(name_sects)] = model.DecimalField(_("".join(['bin ', str(i)])),
            max_digits=6, decimal_places=2)

Bins = type('Bins', (models.Model,), attrs)

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