title: ImportError: No module named flask.ext.sqlalchemy and no solution works
body: <p>I am having trouble in running my code. 
  I did:</p>
  
  <pre><code>from flask_sqlalchemy import SQLAlchemy
  </code></pre>
  
  <p>It keep saying that: ImportError: No module named flask.ext.sqlalchemy</p>
  
  <p>I followed this tutorial: <a href="http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world" rel="nofollow">http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world</a></p>
  
  <p>and it keep getting me lots of import error not only for the sqlalchemy but also these:</p>
  
  <pre><code>from flask.ext.wtf import Form
  from wtforms import TextField, BooleanField
  from wtforms.validators import Required
  </code></pre>
  
  <p>all of above imports got me import errors.
  I had check all similar questions on stack overflow and try all solutions but they did not work. Could someone help me? Thanks in advance.</p>
  
  <p>here is error message:</p>
  
  <pre><code>/Library/Frameworks/Python.framework/Versions/3.5/bin/python3.5    /Users/Mia/Documents/workspace/Assignment3.2/run.py
  Traceback (most recent call last):
    File "/Users/Mia/Documents/workspace/Assignment3.2/run.py", line 1, in &lt;module&gt;
  from app import app
  File "/Users/Mia/Documents/workspace/Assignment3.2/app/__init__.py", line 2, in &lt;module&gt;
  from flask_sqlalchemy import SQLAlchemy
  ImportError: No module named 'flask_sqlalchemy'
  </code></pre>
  
  <p>I felt it's very strange when I check the version of python in my project directory, it's 2.7. But above shows it's 3.5. Will that causing problems?</p>