title: Import module in another directory from a "parallel" sub-directory
body: <p>I want to have a hierarchy that looks like this (and it has to look like this)</p>
  
  <pre><code>main_folder\
      main.py
      domain_sub_directory\
          __init__.py
          domain.py
      ui_sub_direcotory\
          __init__.py
          menu.py
  </code></pre>
  
  <p>I need to activate ui.py frome main.py but then acces domain.py from menu.py. How can I do that ?</p>
  
  <p>I did this in main:</p>
  
  <pre><code>    import ui_sub_directory.ui
  </code></pre>
  
  <p>This in ui:</p>
  
  <pre><code>    import domain_sub_directory.domain
  </code></pre>
  
  <p>But the UI module does not see the domain module.</p>
  
  <p>What am I doing wrong ?</p>
  
  <p>BTW do I need to also import the class I'm working with ? and what is the difference between this and:</p>
  
  <pre><code>from x import y 
  </code></pre>
  
  <p>?</p>
  
  <p><strong>* Edit *</strong> for those who don't understand I want to import from:</p>
  
  <pre><code>folder1 /folder2 /folder3 /module1 
  </code></pre>
  
  <p>I want to import this:</p>
  
  <pre><code>folder1 /folder2 /module2
  </code></pre>