title: How to read a large file - line by line?
body: <p>I want to iterate over each line of an entire file. One way to do this is by reading the entire file, saving it to a list, then going over the line of interest. This method uses a lot of memory, so I am looking for an alternative.</p>
  
  <p>My code so far:</p>
  
  <pre><code>for each_line in fileinput.input(input_file):
      do_something(each_line)
  
      for each_line_again in fileinput.input(input_file):
          do_something(each_line_again)
  </code></pre>
  
  <p>Executing this code gives an error message: <code>device active</code>.</p>
  
  <p>Any suggestions?</p>
  
  <p>The purpose is to calculate pair-wise string similarity, meaning for each line in file, I want to calculate the Levenshtein distance with every other line.</p>