title: In python, if a function doesn't have a return statement, what does it return?
body: <p>Given this example function:</p>
  
  <pre><code>def writeFile(listLine,fileName):
      '''put a list of str-line into a file named fileName'''
      with open(fileName,'a',encoding = 'utf-8') as f:
          for line in listLine:
              f.writelines(line+'\r\n')
      return True
  </code></pre>
  
  <p>Does this <code>return True</code> statement do anything useful?</p>
  
  <p>What's the difference between with it and without it? What would happen if there were no return function?</p>