title: Update Existing Document : Mongo Alchemy
body: <p>I need some help with MongoAlchemy. I'm trying to create a web application with python, flask, Mongo DM and Mongo Alchemy (as an object document mapper) and I'm struggling with updating existing documents. </p>
  
  <p>My problem is that I cannot update an existing document through it's object Id. Below I'm attaching my def for updating</p>
  
  <pre><code>@app.route('/update', methods =[ 'GET', 'POST' ])    
   def update():
       if request.method == 'POST':
           id = request.form['object_id'] # Getting values with html
           patientzero = BloodDoonor.query.get_or_404(id) 
           first_name = request.form['name']# Getting values with htmlform
           last_name = request.form['surname']# Getting values with html form
           blood_type = request.form['blood_type']# Getting values with html                
           update_record = BloodDoonor.patientzero.update(BloodDoonor.last_name = last_name)
       return render_template('update.html', result = result)
  </code></pre>
  
  <p>And flask gives me that error:</p>
  
  <blockquote>
    <p>AttributeError AttributeError: type
    object 'BloodDoonor' has no attribute 'patientzero'</p>
  </blockquote>
  
  <p>I'm very new to Python and not very good in code. Please forgive me for the sloppy description I gave above. Any help would be appreciated.</p>