Question

我正在尝试按照本教程https://www.codementor.io/olawalealadeusi896/restful-api-with-python-flask-framework-and-postgres-db-part-1-kbrwbygx5制作应用但是我一直坚持使用“ python manage.py db migration”运行迁移。我遇到了这个错误，无法识别它们的含义，也不知道如何解决这个问题，因为我是python的新手。

FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True or False to suppress this warning.

'SQLALCHEMY_TRACK_MODIFICATIONS增加了大量开销，并且'

Traceback (most recent call last):
  File "manage.py", line 17, in <module>
    manager.run()
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/flask_script/__init__.py", line 417, in run
    result = self.handle(argv[0], argv[1:])
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/flask_script/__init__.py", line 386, in handle
    res = handle(*args, **config)
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/flask_script/commands.py", line 216, in __call__
    return self.run(*args, **kwargs)
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/flask_migrate/__init__.py", line 95, in wrapped
    f(*args, **kwargs)
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/flask_migrate/__init__.py", line 215, in migrate
    version_path=version_path, rev_id=rev_id)
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/alembic/command.py", line 214, in revision
    script_directory.run_env()
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/alembic/script/base.py", line 489, in run_env
    util.load_python_file(self.dir, "env.py")
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
    module = load_module_py(module_id, path)
  File "/home/jebbyk/.local/share/virtualenvs/blog_rest-pkqspueH/lib/python3.6/site-packages/alembic/util/compat.py", line 173, in load_module_py
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "migrations/env.py", line 27, in <module>
    'SQLALCHEMY_DATABASE_URI').replace('%', '%%'))
AttributeError: 'NoneType' object has no attribute 'replace'

这似乎是迁移> env.py

中此行的主要问题

config.set_main_option('sqlalchemy.url', current_app.config.get('SQLALCHEMY_DATABASE_URI').replace('%', '%%'))

但是运行“ python manage.py db init”后会自动生成“ migrations”目录而且我不确定它是否包含任何错误

Answer 1

在your example之后。 SQLALCHEMY_DATABASE_URI variable get from system environment

SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL')

所以。您需要从终端运行以下命令来设置系统环境变量

$ export DATABASE_URL= postgres://name:password@houst:port/blog_api_db

Answer 2

发生这种情况是因为您可能使用 sqlalchemy.engine.url.URL 类来创建数据库 url。它不会给你回字符串。而是 <class 'sqlalchemy.engine.url.URL'> 的对象。

解决方案

为避免错误，请在正在使用的迁移/env.py 中找到配置

current_app.config.get('SQLALCHEMY_DATABASE_URI')

并将其替换为：

str(current_app.config.get('SQLALCHEMY_DATABASE_URI'))

迁移将正常工作。

烧瓶，不能迁移。 'SQLALCHEMY_DATABASE_URI'）。replace（'％'，'%%'））AttributeError：'NoneType'对象没有属性'replace'

2 个答案: