title: convert string into 2 dimensional list with no imports
body: <p>I need to convert a string representation into a 2 dimensional list.</p>
  <p>I am trying to read inputs from a text file. All inputs follow a standard format where each line represents a different variable. When I read the following line from the input file using f.readline():</p>
  <pre><code>[[0, 2, 1, 2, 3, 0], [2, 0, 3, 0, 1, 0], [2, 0, 0, 3, 3, 0], [0, 2, 3, 0, 0, 3], [1, 2, 3, 1, 0, 2], [2, 1, 0, 1, 3, 0]]
  </code></pre>
  <p>This line is read in as a string, but I need it converted to a 2 dimensional list. A constraint for this project is I cannot use any packages, only base python.</p>
  <p>How do I do this?</p>