Django model.foreignKey and return self.text errors

Question

So I'm working on the model.py in Django and i'm getting 2 pylint errors. I don't understand why? is this an issue with pylint or something i'm doing wrong in my code.

E1120:No value for argument 'on_delete' in constructor call    
E1136:Value 'self.text' is unsubscriptable

The first is on line 19, in Entry topic = models.ForeignKey(Topic)
The second is on line 24 self.text[:50]

If I remove the entry class the code works

from django.db import models

# Create your models here.
class Topic(models.Model):
"""A topic the user is learning about"""
text = models.CharField(max_length=200)
date_added = models.DateTimeField(auto_now_add=True)

def __str__(self):
    """Return a string representation of the model."""
    return self.text

class Entry(models.Model):
"""Something specific learned about a topic"""
topic = models.ForeignKey(Topic)
text = models.TextField()
date_added = models.DateTimeField(auto_now_add=True)

class Meta:
    verbose_name_plural = "entries"

def __str__(self):
    """Return a string representation of the model."""
    return self.text[:50] + "..."

https://stackoverflow.com/questions/4617674/what-does-it-mean-for-an-object-to-be-unscriptable — dfundako, Feb 15 '18 at 15:07
https://stackoverflow.com/questions/38388423/what-does-on-delete-do-on-django-models — dfundako, Feb 15 '18 at 15:07

score 7 · Accepted Answer · answered Feb 15 '18 at 21:45

7

The problem was ForeignKey in Django 1.9 required 1 positional argument in Django 2.0 ForeignKey 2 required positional argument

  topic = models.ForeignKey("Topic", on_delete=models.PROTECT)

answered Feb 15 '18 at 21:45

mayhemds

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I'm facing the same issue. How did you resolve the "self.text is unsubscriptable" issue? This answer does not resolve that problem. – Jeff Moorhead Apr 02 '18 at 16:27
I removed the set number and left it blank. Not ideal but it worked. – mayhemds Apr 08 '18 at 14:59
1

I see you're learning from 'Python Crash Course'. Great choice. Used it myself. The reason `return self.text[:50] + "..."` isn't working is because Python doesn't recognize `self.text` as a String (because it's really a `models.TextField`) so it doesn't know how to interpret `[:50]` or how to concatenate it with `"..."`. When you get rid of the other stuff it knows to just cast it as a String, that's why that works. To get it to work as intended try `return str(self.text)[:50] + "..."`. That way `self.text` is now represented in its String form and you can perform String operations on it. – cbender Oct 30 '18 at 19:02

score 0 · Answer 2 · edited Feb 20 '19 at 06:45

0

The reason of second issue is you missed the command after the command python manage.py makemigrations [appname], the missing command is python manage.py migrate.

edited Feb 20 '19 at 06:45

Serenity

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answered Feb 20 '19 at 06:25

Gavin.Hall

1

score 0 · Answer 3 · answered Sep 10 '19 at 08:23

To prevent this, we should use on_delete=models.PROTECT.

By default Django uses on_delete=models.CASCADE but this is not secure if object deleted accidentally.

In that case there would be no notification of deleted objects so it would be ideal to use models.PROTECT.

Django model.foreignKey and return self.text errors

3 Answers3

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