NoneType' object has no attribute 'items
<p>I don't really know where I went wrong. Can you please help me? I keep getting this error when uploading the code to school correction system.</p>

<pre><code>  -- test: 1
  -- failed

  -- standard error
  Traceback (most recent call last):
    File "/proc/self/fd/3", line 6, in &lt;module&gt;
      print(sorted(new_dict.items()))
  AttributeError: 'NoneType' object has no attribute 'items'
  --
  -- exit code: 1
                (anything other than 0 indicates an error)
                (all scripts are killed after three seconds)

  -- expected standard output
  [(4, 'a'), (10, 'c')]
  --

  -- actual standard output (max 200 lines)
  [(4, 'a'), (10, 'c')]
  --
</code></pre>

<p>My code is:</p>

<pre><code>import sys

def swap_unique_keys_values(n):
    d = {}
    for i in n:
        if not n[i] in d:
            d[n[i]] = i
        else:
            del d[n[i]]
    print(sorted(d.items()))

def main():
    swap_unique_keys_values(sys.argv[1])

if __name__ == '__main__':
    main()
</code></pre>

<p>The input is a dictionary. Any help is really appreciated.</p>