title: if block in python not executed with True statement
body: <p>I just started learning python with small scripts. I came across a quiz to determine a list to be symmetric if the first row is the same as the first column,
  the second row is the same as the second column and so on. </p>
  
  <pre><code>def symmetric(block):
      n = len(block)
      i = 0
      for i in range(n-1):
          j = 0
          for j in range(n-1):
              if (block[i][j] != block[j][i]):
                  return False
              j +=1
          i +=1
      return True
  </code></pre>
  
  <p>So the result of</p>
  
  <pre><code>print symmetric([["cat", "dog", "fish"],
                  ["dog", "dog", "dog"],
                  ["fish","fish","cat"]])
  </code></pre>
  
  <p>should be False. </p>
  
  <p>However, this code always return True, and in debugger I can see <code>block[i][j] != block[j][i]</code> returns True but the if block is not executed. Is there anything wrong with the comparison or the if block is not correctly composed?</p>