ImportError:virtualenv中没有名为flask.ext.sqlalchemy的模块

Question

以下是我在尝试从flask_sqlalchemy import sqlalchemy在python3中运行以下代码时遇到的主要错误

Traceback (most recent call last):
  File "/home/jsnyder10/.local/bin/flask", line 11, in <module>
sys.exit(main())
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 513, in main
cli.main(args=args, prog_name=name)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 380, in main
return AppGroup.main(self, *args, **kwargs)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/click/core.py", line 697, in main
rv = self.invoke(ctx)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/click/core.py", line 1066, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/click/core.py", line 895, in invoke
return ctx.invoke(self.callback, **ctx.params)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/click/core.py", line 535, in invoke
return callback(*args, **kwargs)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/click/decorators.py", line 64, in new_func
return ctx.invoke(f, obj, *args[1:], **kwargs)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/click/core.py", line 535, in invoke
return callback(*args, **kwargs)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 423, in run_command
app = DispatchingApp(info.load_app, use_eager_loading=eager_loading)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 152, in __init__
self._load_unlocked()
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 176, in _load_unlocked
self._app = rv = self.loader()
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 237, in load_app
rv = locate_app(self.app_import_path)
  File "/home/jsnyder10/.local/lib/python3.5/site-packages/flask/cli.py", line 90, in locate_app
__import__(module)
  File "/home/jsnyder10/Documents/CS50/pset7/pset7/finance/application.py", line 2, in <module>
from flask_sqlalchemy import SQLAlchemy
ImportError: No module named 'flask_sqlalchemy'

不确定它是否相关，但当我更新sqlaclhemy时，它给出了以下pip提示。我尝试过更新pip，但由于某些原因，9.0.1版说它已升级，但实际上没有更新。

You are using pip version 8.1.1, however version 9.0.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

下面是我运行pip列表时得到的结果，您可以看到sqlalchemy和flask sqlalchemy都已安装。

DEPRECATION: The default format will switch to columns in the future. You can use --format=(legacy|columns) (or define a format=(legacy|columns) in your pip.conf under the [list] section) to disable this warning.
appdirs (1.4.3)
click (6.7)
Flask (0.12.1)
Flask-SQLAlchemy (2.2)
itsdangerous (0.24)
Jinja2 (2.9.6)
MarkupSafe (1.0)
packaging (16.8)
pip (9.0.1)
pyparsing (2.2.0)
setuptools (35.0.2)
six (1.10.0)
SQLAlchemy (1.1.9)
Werkzeug (0.12.1)
wheel (0.29.0)

我猜它使用了不正确的Python版本。我从来没有弄清楚这件事的真相，但我用核武器攻击了我的虚拟机，并制造了一个新的虚拟机来修复它。谢谢你们的帮助，希望我能把它修好。

Answer 1

尝试此pip安装sqlalchemy

Answer 2

而不是：

  from flask.ext.mongoalchemy import MongoAlchemy

使用：

  from flask_mongoalchemy import MongoAlchemy

Answer 3

导入语句：

from flask.ext.sqlalchemy import SQLAlchemy

引发异常重要错误：由于扩展代码不再存储在flask.ext下，因此在viralenv中没有名为flask.ext.sqlalchemy的模块。

因此，导入语句应更改为：

from flask_sqlalchemy import SQLAlchemy