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python - Django：save() 缺少 1 个必需的位置参数：'self'

问题描述

我正在尝试覆盖 save 方法，我想我写的正是文档所说的，但是得到了错误

from django.db import models

class Post(models.Model):
    name = models.CharField(max_length = 20)
    lower_name = models.CharField(max_length = 20)

    def save(self, *args, **kwargs):
        if not self.lower_name:
            self.lower_name = self.name.lower()
        super().save(*args, **kwargs)

这是我调用 python manage.py migrate 时的回溯

(project_site) λ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions, works
Running migrations:
  Applying works.0018_post_url_name...Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\core\management\__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\core\management\__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\core\management\base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\core\management\base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\core\management\base.py", line 83, in wrapped
    res = handle_func(*args, **kwargs)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\core\management\commands\migrate.py", line 234, in handle
    fake_initial=fake_initial,
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\migrations\executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\migrations\executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\migrations\executor.py", line 245, in apply_migration
    state = migration.apply(state, schema_editor)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\migrations\migration.py", line 124, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\migrations\operations\fields.py", line 112, in database_forwards
    field,
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\backends\sqlite3\schema.py", line 327, in add_field

    self._remake_table(model, create_field=field)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\backends\sqlite3\schema.py", line 188, in _remake_table
    self.effective_default(create_field)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\backends\base\schema.py", line 233, in effective_default
    return field.get_db_prep_save(self._effective_default(field), self.connection)
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\backends\base\schema.py", line 212, in _effective_default
    default = field.get_default()
  File "D:\Code\Python\project_site\.venv\lib\site-packages\django\db\models\fields\__init__.py", line 797, in get_default
    return self._get_default()
TypeError: save() missing 1 required positional argument: 'self'

python版本：3.6.8 django版本：2.2.4

标签： pythondjango

解决方案

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