Django Model __unicode__记录时引发异常 [英] Django Model __unicode__ raising exception when logging

问题描述

我有一个模型类，如下所示:

I have a model class that looks like the following:

class Address(models.Model):
    # taking length of address/city fields from existing UserProfile model
    address_1 = models.CharField(max_length=128,
                                 blank=False,
                                 null=False)

    address_2 = models.CharField(max_length=128,
                                 blank=True,
                                 null=True)

    address_3 = models.CharField(max_length=128,
                                 blank=True,
                                 null=True)

    unit = models.CharField(max_length=10,
                            blank=True,
                            null=True)

    city = models.CharField(max_length=128,
                            blank=False,
                            null=False)

    state_or_province = models.ForeignKey(StateOrProvince)

    postal_code = models.CharField(max_length=20,
                                   blank=False,
                                   null=False)

    phone = models.CharField(max_length=20,
                             blank=True,
                             null=True)

    is_deleted = models.BooleanField(default=False,
                                     null=False)

    def __unicode__(self):
        return u"{}, {} {}, {}".format(
            self.city, self.state_or_province.postal_abbrev, self.postal_code, self.address_1)

键是__unicode__方法.我有一个具有此表的外键字段的客户模型，并且正在执行以下日志记录:

The key being the __unicode__ method. I have a customer model that has a foreign key field to this table, and I am doing the following logging:

log.debug(u'Generated customer [{}]'.format(vars(customer)))

这很好，但是如果address_1字段值包含非ASCII值，请说

This works fine, but if an address_1 field value contains a non ascii value, say

57562VånNess Hwy

57562 Vån Ness Hwy

系统抛出以下异常:

UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 345: ordinal not in range(128)

我在django/db/models/base.py中找到了一个奇怪的方法:

I tracked this down to a strange method in django/db/models/base.py:

def __repr__(self):
        try:
            u = six.text_type(self)
        except (UnicodeEncodeError, UnicodeDecodeError):
            u = '[Bad Unicode data]'
        return force_str('<%s: %s>' % (self.__class__.__name__, u))

如您所见，

该方法被调用为force_str，该方法未正确处理.这是一个错误吗?如果在我的对象上调用了unicode，不是所有内容都应该在unicode中吗?

as you can see, this method is getting called to force_str, which doesn't get handled correctly. is this a bug? if unicode is getting called on my object, shouldn't everything be in unicode?

推荐答案

根据

According to the docs, when a python object is passed as an argument to '{}'.format(obj),

通常的约定是，[{}内的空格式字符串(")会产生 就像您在值上调用str()一样.

A general convention is that an empty format string ("") [within the "{}"] produces the same result as if you had called str() on the value.

这意味着您正在有效地调用str(vars(customer))，并且vars(customer)返回一个dict.

This means you're effectively calling str(vars(customer)), and vars(customer) returns a dict.

在dict上调用str()会在其键和值上调用repr()，因为否则您将获得模棱两可的输出(例如str(1) == str('1') == '1'但repr(1) == '1' and repr('1') == '"1"'(请参阅Python中__str__和__repr__之间的区别)

Calling str() on a dict will call repr() on its keys and values because otherwise you'd get ambiguous output (eg str(1) == str('1') == '1' but repr(1) == '1' and repr('1') == '"1"' (see Difference between __str__ and __repr__ in Python)

因此repr()仍在您的Address上被调用，这将返回一个字符串.

Therefore repr() is still being called on your Address, which returns a string.

现在在Python 2中不允许从repr()返回unicode- https://stackoverflow.com/a/3627835/648176 ，因此您需要在模型中覆盖__str__()，以使其能够处理解码为ascii(

Now returning unicode from repr() is not allowed in Python 2 - https://stackoverflow.com/a/3627835/648176, so you'll need to either override __str__() in your model to make it handle decoding into ascii (Django docs), or do something like:

string_dict = {str(k): str(v) for (k, v) in vars(customer).items()}
log.debug(u'Generated customer [{}]'.format(string_dict))

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