ImportError: No module named flask.ext.sqlalchemy in virtualenv

Question

Here is the main error I get when trying to run the following code in python3 from flask_sqlalchemy import SQLAlchemy

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'

Not sure if it is related but when I update sqlaclhemy it gives the following pip heads up. I tried updating pip, but for some reason version 9.0.1 says it is upgraded but doesn't actually update.

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.

Here is what I get when I run pip list, as you can see both sqlalchemy and flask-sqlalchemy are installed.

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)

I'm guessing it was using the incorrect Python version. I never got to the bottom of this, but nuking my virtual machine and making a new one fixed it. Thanks for the help guys, wish I could have fixed it.

Answer 1

The import statement:

from flask.ext.sqlalchemy import SQLAlchemy

raises the exception ImportError: No module named flask.ext.sqlalchemy in virtualenv since the extension code is no longer stored under flask.ext, as stated in this answer.

Therefore, the import statement should be changed to:

from flask_sqlalchemy import SQLAlchemy

Answer 2

I have the same problem, I'm using Flask-WhooshAlchemy (0.56) extension, but if you try to import it: import flask_whooshalchemy as whooshalchemy that gives the reported error: ImportError: No module named flask.ext.sqlalchemy.

Then I have changed the import statement in Flask-WhooshAlchemy (line 18) from import flask.ext.sqlalchemy as flask_sqlalchemy to import flask_sqlalchemy as flask_sqlalchemy # Modified.

That solve the import error, but that means that you have a modified version of Flask-WhooshAlchemy.