python_2_unicode_compatible error; python 2.7, django 1.9

Question

I am using Python 2.7 and Django 1.9.7. I am trying to add a string method to models.py but I'm getting an error. When I run "python manage.py runserver", I get the following:

ValueError: @python_2_unicode_compatible cannot be applied to Languages because it doesn't define __ str__().

from django.db import models
from django.utils.encoding import python_2_unicode_compatible

@python_2_unicode_compatible
class Languages(models.Model):
    langid = models.AutoField(db_column='LangID', primary_key=True)
    lname = models.CharField(db_column='lName', max_length=50, blank=True, null=True)

    class Meta:
        db_table = 'languages'

    def __str__(self):
        return self.lname

This is very similar to the following Question: python_2_unicode_compatible error

But the problem there was that Django was not a new enough version. Clearly there is something different going on here. Any ideas on what the problem might be?

your snippet works fine on my computer. maybe try using 4 spaces instead of blank lines (say between lname and class Meta and before the definition of str) — Ringil
– Ringil, Commented Jun 15, 2016 at 19:14
@Ringil thanks, I checked but it doesn't seem to be an indentation problem. — Addie
– Addie, Commented Jun 15, 2016 at 19:46

Ankush Raghuvanshi · Accepted Answer · 2016-06-15 19:34:53Z

2

When you are writing

    def __str__(self):
        return self.lname

Then you are over-riding the in-built 'str' method. So whenever str is used, your defined method is called instead of the in-built one.

So if you all you want to do is to return the "lname" of the object of the model "Languages", then you can use a different name of the def like this

    def lang_name(self):
        return u'%s' % self.lname

This u'%s' solves your problem of unicode to string.

Now, if you don't want to use other name of the def, but want to override the in-built 'str' function, then the below should work for you:

    def __str__(self):
        return u'%s' % self.lname

Though, by default Django models have the following function, which returns the default value for an object:

    def __unicode__(self):
        return u'%s' % self.lname

answered Jun 15, 2016 at 19:34

Ankush Raghuvanshi

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2 Comments

Addie Over a year ago

Thanks, this gives me an error though: "TypeError: 'class Meta' got invalid attribute(s): lang_name". Also the Django official tutorial documentation gave me the original code for def __ str__(self): return self.lname docs.djangoproject.com/en/1.9/intro/tutorial02

Ankush Raghuvanshi Over a year ago

def lang_name(self): needs to be defined in the model and not under the Meta class as it is a property of the object of that model. Whereas in class Meta, you define representation (example -> ordering of objects, verbose_name etc) of the objects and not where you decide a new property for the objects See this -> stackoverflow.com/questions/26564001/… There are some pre-defined Meta options which you can use -> docs.djangoproject.com/en/dev/ref/models/options

Ivan_ug · Accepted Answer · 2017-07-26 06:17:52Z

1

I solved this by simply restarting the server.

Ctrl+C

and thereafter;

python manage.py runserver

answered Jul 26, 2017 at 6:17

Ivan_ug

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