title: SQLALCHEMY initiate model class constructor (__init__) after query
body: <p>I Have a simple SQLALCHEMY Model like:</p>
  
  <pre><code>class User(db.Model):
       """ User Model for storing user related details """
       __tablename__ = "users"
  
       UserID = db.Column(db.Integer, primary_key=True, autoincrement=True)
       Email = db.Column(db.String(255), unique=True, nullable=False)
       UserName = db.Column(db.String(255), unique=True, nullable=False)
       Password = db.Column(db.String(255), nullable=False)
       #bla....
  
       def __init__(self, email, username, password):
            # private
           self.__private = 'testing'
           # bla...
  
       def test(self):
           print self.__private
  
      # bla....
  </code></pre>
  
  <p>and in my app I do a simple query:</p>
  
  <pre><code>user = User.query.filter((User.Email == req_email) | (User.UserName == req_username)).first()
  </code></pre>
  
  <p>problem: when i call</p>
  
  <pre><code>user.test()
  </code></pre>
  
  <p>it throws me error: </p>
  
  <blockquote>
    <p>'User' object has no attribute '_User__private'</p>
  </blockquote>
  
  <p>, because my private variable never been initialize in <strong>init</strong> function.</p>
  
  <p>question: so, how to initiate class model after query called?</p>