Django执行migrate/runserver报错：settings.DATABASES缺失ENGINE配置

无法迁移代码变更，执行python manage.py runserver命令时触发报错，完整报错栈如下：

Traceback (most recent call last):
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\manage.py", line 22, in 
main()
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\manage.py", line 18, in main
execute_from_command_line(sys.argv)
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\core\management\__init__.py", line 442, in
execute_from_command_line
utility.execute()
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\core\management\__init__.py", line 436, in
execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\core\management\base.py", line 413, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\core\management\base.py", line 459, in execute
output = self.handle(*args, **options)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\core\management\base.py", line 107, in wrapper
res = handle_func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\core\management\commands\migrate.py", line
117, in handle
executor = MigrationExecutor(connection, self.migration_progress_callback)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\migrations\executor.py", line 18, in __init__
self.loader = MigrationLoader(self.connection)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\migrations\loader.py", line 58, in __init__
self.build_graph()
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\migrations\loader.py", line 235, in build_graph
self.applied_migrations = recorder.applied_migrations()
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\migrations\recorder.py", line 89, in applied_migrations
if self.has_table():
^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\migrations\recorder.py", line 63, in has_table
with self.connection.cursor() as cursor:
^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\utils\asyncio.py", line 26, in inner
return func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\backends\base\base.py", line 316, in cursor
return self._cursor()
^^^^^^^^^^^^^^
File "C:\Users\kshitijb\Desktop\Income-Expense-Tracker\env\Lib\site-packages\django\db\backends\dummy\base.py", line 20, in complain
raise ImproperlyConfigured(
django.core.exceptions.ImproperlyConfigured: settings.DATABASES配置不正确，请提供ENGINE值。更多详情请查看settings文档。

当前配置 #

settings.py相关代码 #

DB_NAME = os.environ.get("POSTGRES_DB") #数据库名称
DB_USER_PASSWORD = os.environ.get("POSTGRES_PASSWORD") #数据库用户密码
DB_USER = os.environ.get("POSTGRES_USER") #数据库用户名
DB_HOST = os.environ.get("POSTGRES_HOST") #数据库主机
# POSTGRES_PORT = os.environ.get("POSTGRES_PORT") #数据库端口


POSTGRES_READY = (
    DB_NAME is not None
    and DB_USER_PASSWORD is not None
    and DB_USER is not None
    and DB_HOST is not None
)

print(POSTGRES_READY)

if POSTGRES_READY:
    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.postgresql',
            'NAME': DB_NAME,
            'USER': DB_USER,
            'PASSWORD': DB_USER_PASSWORD,
            'HOST': DB_HOST,
        }
    }

.env文件内容 #

export DB_NAME=<DB_NAME>
export DB_USER=<DB_USER>
export DB_USER_PASSWORD=<DB_USER_PASSWORD>
export DB_HOST=localhost

export CLOUD_NAME=<CLOUDINARY_CLOUD_NAME>
export API_KEY=<CLOUDINARY_API_KEY>
export API_SECRET=<CLOUDINARY_API_SECRET>
export SECRET_KEY=<CLOUDINARY_SECRET_KEY>
export SENTRY_DSN='<SENTRY_DSN_URL>'

问题原因及解决方法 #

核心问题 #

settings.py中读取的环境变量名称与.env里定义的完全不匹配：

• settings.py用POSTGRES_DB，但.env里是DB_NAME
• settings.py用POSTGRES_PASSWORD，但.env里是DB_USER_PASSWORD
• settings.py用POSTGRES_USER，但.env里是DB_USER
• settings.py用POSTGRES_HOST，但.env里是DB_HOST

这导致所有环境变量读取结果为None，POSTGRES_READY为False，DATABASES未被赋值，Django默认使用dummy数据库引擎，从而触发配置错误。

修复步骤 #

1. 统一环境变量名称
   选择修改settings.py匹配.env的变量名，修改后的代码如下：

   DB_NAME = os.environ.get("DB_NAME") #数据库名称
   DB_USER_PASSWORD = os.environ.get("DB_USER_PASSWORD") #数据库用户密码
   DB_USER = os.environ.get("DB_USER") #数据库用户名
   DB_HOST = os.environ.get("DB_HOST") #数据库主机
   

2. 修正.env文件格式（Windows环境）
   Windows的cmd/powershell不支持export命令，需去掉所有export前缀，改为纯键值对格式：

   DB_NAME=<DB_NAME>
   DB_USER=<DB_USER>
   DB_USER_PASSWORD=<DB_USER_PASSWORD>
   DB_HOST=localhost
   
   CLOUD_NAME=<CLOUDINARY_CLOUD_NAME>
   API_KEY=<CLOUDINARY_API_KEY>
   API_SECRET=<CLOUDINARY_API_SECRET>
   SECRET_KEY=<CLOUDINARY_SECRET_KEY>
   SENTRY_DSN='<SENTRY_DSN_URL>'
   

3. 确保.env文件被正确加载
   安装python-dotenv包：

   pip install python-dotenv
   

   在manage.py文件开头添加加载代码：

   from dotenv import load_dotenv
   load_dotenv()
   

4. 验证配置
   运行命令进入Django shell：

   python manage.py shell
   

   输入以下代码检查环境变量是否正确读取：

   import os
   print(os.environ.get("DB_NAME"))
   print(os.environ.get("DB_USER"))
   print(os.environ.get("DB_USER_PASSWORD"))
   print(os.environ.get("DB_HOST"))
   

   同时检查POSTGRES_READY的值是否为True。

内容的提问来源于stack exchange，提问作者kshitij bramhecha