title: Change text of QLineEdit from another class
body: <p>I have 2 classes : MainWindow() and ModelSelection().</p>
  
  <p>I would like to access a <code>QLineEdit</code> which is declared in MainWindow() from ModelSelection() in order to change the text of the <code>QLineEdit</code> thanks to the method <code>setText()</code>.</p>
  
  <p><strong>mainWindow.py</strong></p>
  
  <pre><code>from modelSelection import ModelSelection
  
  def __init__(self, workingDir, filename, mode, tabAnalysis, parent=None):
      super(MainWindow,self).__init__(parent)
      self.fileLine = QLineEdit()
  </code></pre>
  
  <p><strong>modelSelection.py</strong></p>
  
  <pre><code>import mainWindow    
  
  def openModelDialog(self):
      self.filename = QFileDialog.getOpenFileName(self, "Open File",filePath,"(*.txt)")
  
      if self.filename:
          mainWindow.fileLine.setText(self.filename[0])
      return self.filename
  </code></pre>
  
  <p>It returns : <code>AttributeError: 'module' object has no attribute 'fileLine'</code></p>