title: No removal of null values (Python)
body: <p>For processing the content of multiple CSV files, I have to filter several characters, most notably NULL values, from string-list-elements. For this I've tried several solutions from the web. One of them is the following function:</p>
  
  <pre><code>def removeNull(rawString):
      l = filter("\u0000", list(rawString))
      newString = ''.join(l)
      printUtil.printAll(newString, "\n")
      return newString
  </code></pre>
  
  <p>However, it always gives me <code>TypeError: 'str' object is not callable</code>, terminating the program. The more sophisticated solutions didn't gave me an error but they changed absolutely nothing and the NULL values where still in place. </p>
  
  <p>Furthermore, if I exchange <code>\u0000</code> by any other value but <code>None</code> (which results in no changes), I am getting the same error message.</p>
  
  <p>Hopefully, someone can solve this for me for I am out of ideas after 4 or 5 hours of trial and error.</p>
  
  <p>Thank you for your answers and suggestions!</p>
  
  <p><strong>Solving the problem:</strong></p>
  
  <p>The error message originated from the fact, that I used <code>"\u0000"</code> as argument for the build in filter-function. Two valid solutions to that particular problem focus on passing the necessary function:</p>
  
  <pre><code>l = filter(lambda x: x != '\u0000',rawString)
  </code></pre>
  
  <p>or</p>
  
  <pre><code>l = filter(lambda x:ord(x) != 0, list(rawString))
  </code></pre>