title: what is "{:<20}" format_string meaning in python?
body: <p>What does {:&lt;20} {:>4}  mean in format_string？</p>
  
  <p>Beginner</p>
  
  <pre><code>popularity = [["Language", 2017, 2012, 2007, 2002, 1997, 1992, 1987], 
            ["Java", 1, 2, 1, 1, 15, 0, 0],
            ["C", 2, 1, 2, 2, 1, 1, 1],
            ["C++", 3, 3, 3, 3, 2, 2, 5],
            ["C#", 4, 4, 7, 13, 0, 0, 0],
            ["Python", 5, 7, 6, 11, 27, 0, 0],
            ["Visual Basic .NET", 6, 17, 0, 0, 0, 0, 0],
            ["PHP", 7, 6, 4, 5, 0, 0, 0],
            ["JavaScript", 8, 9, 8, 7, 23, 0, 0],
            ["Perl", 9, 8, 5, 4, 4, 10, 0]]
  
  format_string = "{:&lt;20}  {:&gt;4}  {:&gt;4}  {:&gt;4}  {:&gt;4}  {:&gt;4}  {:&gt;4}  {:&gt;4}"
  </code></pre>