title: Delete the duplicate arrays inside an array in python
body: <p>I want to ignore the duplicates from an array that has multiple array in lowest running cost. For example;</p>
  
  <pre><code>A = [['1','2'],['3','4'],['5','6'],['1','2'],['3','4'],['7','8']]
  </code></pre>
  
  <p>the expected output should be like as</p>
  
  <pre><code>Output = [['1','2'],['3','4'],['5','6'],['7','8']]
  </code></pre>
  
  <p>Is it possible to compare arrays inside an array.
  I am doing in this way; </p>
  
  <pre><code> A = [['1','2'],['3','4'],['5','6'],['1','2'],['3','4'],['7','8']]
          output = set()
          for x in A:
              output.add(x)
          print (output)
  </code></pre>
  
  <p>But it prompts;</p>
  
  <blockquote>
    <p>TypeError: unhashable type: 'list'</p>
  </blockquote>