Django 1.7 ValueError: invalid literal for int() with base 10: 'a'

Question

I am getting this error:

    Operations to perform:
  Apply all migrations: account, jobs, assets, sessions, admin, auth, laptops, contenttypes, mardes
Running migrations:
  Applying assets.0004_auto_20150202_1707...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 338, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 160, in handle
    executor.migrate(targets, plan, fake=options.get("fake", False))
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 63, in migrate
    self.apply_migration(migration, fake=fake)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 97, in apply_migration
    migration.apply(project_state, schema_editor)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 107, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 37, in database_forwards
    field,
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/schema.py", line 42, in add_field
    super(DatabaseSchemaEditor, self).add_field(model, field)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 397, in add_field
    definition, params = self.column_sql(model, field, include_default=True)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 120, in column_sql
    default_value = self.effective_default(field)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 183, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py", line 1722, in get_db_prep_save
    return self.related_field.get_db_prep_save(value, connection=connection)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 627, in get_db_prep_save
    prepared=False)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 907, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/__init__.py", line 915, in get_prep_value
    return int(value)
ValueError: invalid literal for int() with base 10: 'a'

When running python manage.py migrate.

For this app there is only an admin.py and models.py file, everything else is blank. Here is the models.py file:

from django.db import models
from django.contrib.auth.models import User

class Asset_type(models.Model):
    name = models.CharField(max_length=50)

    def __str__(self):
        return self.name

class Asset_os(models.Model):
    name = models.CharField(max_length=50)

    def __str__(self):
        return self.name

class Asset_cs_status(models.Model):
    status = models.CharField(max_length=50)

    def __str__(self):
        return self.status

class Asset_floor(models.Model):
    name = models.CharField(max_length=50)

    def __str__(self):
        return self.name

class Asset(models.Model):
    DLO = (
            ('0', 'Desktop'),
            ('1', 'Laptop'),
            ('2', 'Other'),
            )
    user = models.ForeignKey(User)
    asset_type = models.ForeignKey(Asset_type)
    asset_os = models.ForeignKey(Asset_os)
    asset_cs_status = models.ForeignKey(Asset_cs_status)
    asset_floor = models.ForeignKey(Asset_floor)
    ppl = models.CharField(max_length=40, unique=True)
    desktop_laptop = models.CharField(max_length=1, choices=DLO) 
    date_of_purchase = models.DateField()
    extra_info = models.CharField(max_length=250, default='-')
    pc_name = models.CharField(max_length=100, null=True, default='-')
    bookable = models.BooleanField(default=False)
    image = models.ImageField(upload_to='asset_files/%Y/%m/%d', null=True, blank=True, help_text='Optional')

    def __str__(self):
        return self.asset_type.name+' ('+self.ppl+')' 

Please let me know if you need to see anything else. BC

Answer 1

Well, something migration fails due to Type mismatch.

e.g. IntegerField may or may not have default value '', something, django migration don't warning you in a consistent way. Give its default value -1 will pass error check in django..

so, general solution is:

1. search type mismatch on default value

if not fixed, then

1. delete model, by adding these magic lines:

operations = [
    migrations.DeleteModel("Your Model Name"),
 ]

2. run makemigration again.

This will drop the old database and create a new one without:

ask any goofy questions 10 times

Did you rename training.g1 to training.haha (a IntegerField)? [y/N]

Answer 2

The solution was found looking in the assets.0004_auto_20150202_1707 file under assets > migrations

It had picked up a default value I had typed in previously. Removing the files and regenerating them solved the problem.