title: NoneType: TypeError: 'tuple' object does not support item assignment
body: <p>I am reading an Excel file with openpyxl and rows are getting parsed as tuple objects. One of the objects in the tuple can be a NoneType. Further in the code rows are compared with other rows. These last rows don't have  a NoneType, but are a empty String object, which hampers the comparison. So I'm using the following code to replace the NoneType by an empty String object.</p>
  <pre><code>                for row in previous_worksheet.iter_rows(values_only=True):
                      print(&quot;row &quot; + str(type(row)))
                      for x in range(len(list(row))):
                          print(type(row[x]))
                          if row[x] is None:
                              print(row[x])
                              row[x] = &quot;&quot;
  </code></pre>
  <p>Running this code gives me the following output:</p>
  <pre><code>row &lt;class 'tuple'&gt;
  &lt;class 'str'&gt;
  &lt;class 'str'&gt;
  &lt;class 'str'&gt;
  &lt;class 'str'&gt;
  &lt;class 'str'&gt;
  &lt;class 'str'&gt;
  &lt;class 'str'&gt;
  &lt;class 'NoneType'&gt;
  None
  Traceback (most recent call last):
    File &quot;C:\PycharmProjects\SecuniaComparer\secunia_comparer.py&quot;, line 187, in &lt;module&gt;
      main()
    File &quot;C:\PycharmProjects\SecuniaComparer\secunia_comparer.py&quot;, line 182, in main
      sc.start_parsing()
    File &quot;C:\PycharmProjects\SecuniaComparer\secunia_comparer.py&quot;, line 71, in start_parsing
      row[x] = &quot;&quot;
  TypeError: 'tuple' object does not support item assignment
  </code></pre>
  <p>The object is a NoneType, but assigning an empty String results in a TypeError for a tuple object. How can I fix this?</p>