title: Blank plot using matplotlib
body: <p>I am doing a course in Python (I do not want them to solve the course questions or anything like that) and in this part, the course gives you a code so that you can visualize through graphics the number of robots (x-axis) and time- steps (y-axis), but when I run the code, it just doesn't graph anything. What should I do?</p>
  <p>Sorry if it's a silly question but I'm not quite good with python visualization.</p>
  <p>Here is some of the code:</p>
  <pre><code>def showPlot1(title, x_label, y_label):
      &quot;&quot;&quot;
      What information does the plot produced by this function tell you?
      &quot;&quot;&quot;
      num_robot_range = range(1, 11)
      times1 = []
      times2 = []
      for num_robots in num_robot_range:
          print(&quot;Plotting&quot;, num_robots, &quot;robots...&quot;)
          times1.append(runSimulation(num_robots, 1.0, 20, 20, 0.8, 20, StandardRobot))
          times2.append(runSimulation(num_robots, 1.0, 20, 20, 0.8, 20, RandomWalkRobot))
      pylab.plot(num_robot_range, times1)
      pylab.plot(num_robot_range, times2)
      pylab.title(title)
      pylab.legend(('StandardRobot', 'RandomWalkRobot'))
      pylab.xlabel(x_label)
      pylab.ylabel(y_label)
      pylab.show()
  
  showPlot1(&quot;Title&quot;, &quot;Number of robots&quot;, &quot;Time-steps&quot;)
  </code></pre>
  <p>Here is what it shows:</p>
  <p><a href="https://i.stack.imgur.com/8vg7E.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8vg7E.png" alt="Plot in blank" /></a></p>
  <p>Here is what it prints:</p>
  <pre><code>Plotting 1 robots...
  801.95
  2019.15
  Plotting 2 robots...
  387.35
  997.35
  Plotting 3 robots...
  256.4
  732.7
  Plotting 4 robots...
  201.3
  430.2
  Plotting 5 robots...
  158.25
  366.3
  Plotting 6 robots...
  133.15
  328.0
  Plotting 7 robots...
  113.65
  276.1
  Plotting 8 robots...
  100.0
  239.9
  Plotting 9 robots...
  85.9
  191.85
  Plotting 10 robots...
  78.1
  162.3
  </code></pre>
  <p>Thanks for your help!</p>