Django “expected string or buffer ” error

Question

I am working on my blog, but when I migrate it gave me an error: "expected string or buffer " error. In the line 22. It is an integral model that collects the view times, I guess maybe it was changed the value in the view.py and that could have trouble modifying models after creating them. So I try to chage default and add other arguments in the view_time , but that does not work. Can someone helps me solve the problem or give me a wise idea to redesign a better database? Here are my codes.

models.py, Article contains view time

class Article(models.Model):
    title = models.CharField(max_length=20)
    content = MarkdownField()
    date = models.DateField()
    description = models.TextField(blank=True)
    article_type = (
        ('Learning', (
            ('Python', 'python'),
            ('Java', 'java'),
        )
        ),
    ('Life', 'life'),
    ('Other', 'other')
)
    type = models.CharField(max_length=20, choices=article_type, blank=True)
    lock = models.BooleanField(default=False)
    view_time = models.IntegerField(default=1)   # line 22 [error occured here]

    def __str__(self):
        return self.title

class Comment(models.Model):
    name = models.CharField(null=True, blank=True, max_length=20)
    comment = models.TextField()
    auto_date = models.DateField(auto_now_add=True)
    belong_to = models.ForeignKey(to=Article, related_name="under_comment", null=True, blank=True)

    def __str__(self):
        return self.name

part of the view.py, When one of the articles is visited, the view_time will be added 1.

def blog_content(request, page_num, error_form=None):
    context = {}
    form = CommentForm
    view_update = Article.objects.get(id=page_num)
    view_update.view_time += 1
    view_update.save()
    context['detail'] = view_update
    comments = Comment.objects.filter(belong_to=view_update)
    context['comments'] = comments
    print(comments.values().count())
    if error_form is not None:
        context['form'] = error_form
    else:
        context['form'] = form
    return render(request, 'blog_content.html', context)

the error is followed

Applying blogapp.0018_comment_date...Traceback (most recent call last):##new added
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 367, in execute_from_command_line
    utility.execute()
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/__init__.py", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/base.py", line 305, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/base.py", line 356, in execute
    output = self.handle(*args, **options)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/core/management/commands/migrate.py", line 202, in handle
    targets, plan, fake=fake, fake_initial=fake_initial
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/executor.py", line 97, in migrate
    state = self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/executor.py", line 132, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/executor.py", line 237, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/migrations/operations/fields.py", line 84, in database_forwards
    field,
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/sqlite3/schema.py", line 231, in add_field
    self._remake_table(model, create_fields=[field])
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/sqlite3/schema.py", line 113, in _remake_table
    self.effective_default(field)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/backends/base/schema.py", line 221, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 755, in get_db_prep_save
    prepared=False)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1280, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1275, in get_prep_value
    return self.to_python(value)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/db/models/fields/__init__.py", line 1237, in to_python
    parsed = parse_date(value)
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/django/utils/dateparse.py", line 60, in parse_date
    match = date_re.match(value)
TypeError: expected string or buffer

This is the blogapp.0018_comment_date file:

# -*- coding: utf-8 -*-
# Generated by Django 1.10 on 2017-07-26 12:19
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('blogapp', '0017_comment'),
    ]

    operations = [
        migrations.AddField(
            model_name='comment',
            name='date',
            field=models.DateField(default=True),
        ),
    ]

Answer 1

choices should be an iterable of tuples. You have a structure of three levels.

Try this:

class Article(models.Model):
    title = models.CharField(max_length=20)
    content = MarkdownField()
    date = models.DateField()
    description = models.TextField(blank=True)
    article_type = (
        ('Learning-Python', 'python'),
        ('Learning-Java', 'java'),
        ('Life', 'life'),
        ('Other', 'other')
    )
    type = models.CharField(max_length=20, choices=article_type, blank=True)
    lock = models.BooleanField(default=False)
    view_time = models.IntegerField(default=1)

if you want to add categories to the article_type you will need to add it as an attribute.

Hope this helps.