title: Matplotlib: Multiple legends for contour plot for multiple contour variables
body: <p>I need to make multiple contours plots of several variables on the same page. I can do this with MATLAB (see below for MATLAB code). I cannot get matplotlib to show multiple legends. Any help would be much appreciated.</p>
  
  <p><strong>Python code:</strong></p>
  
  <pre><code>import numpy as np
  from matplotlib import cm as cm
  from matplotlib import pyplot as plt
  
  delta = 0.25
  x = np.arange(-3.0, 3.0, delta)
  y = np.arange(-2.0, 2.0, delta)
  X, Y = np.meshgrid(x, y)
  Z1 = X*np.exp(-X**2-Y**2)
  Z2 = Y*np.exp(-X**2-Y**2)
  
  plt.figure()
  CS = plt.contour(X, Y, Z1, colors='k')
  plt.clabel(CS, inline=1, fontsize=10)
  CS = plt.contour(X, Y, Z2, colors='r')
  plt.clabel(CS, inline=1, fontsize=10)
  plt.legend(['case 1', 'case 2'])
  
  plt.show()
  </code></pre>
  
  <p><strong>MATLAB code:</strong></p>
  
  <pre><code>[X,Y] = meshgrid(-2:.2:2,-2:.2:3);
  Z1 = X.*exp(-X.^2-Y.^2);
  Z2 = Y.*exp(-X.^2-Y.^2);
  
  [C,h] = contour(X,Y,Z1, 'color', 'k');
  set(h,'ShowText','on','TextStep',get(h,'LevelStep')*2);
  hold on
  
  [C,h] = contour(X,Y,Z2, 'color', 'r');
  set(h,'ShowText','on','TextStep',get(h,'LevelStep')*2);
  
  fn = {'case 1', 'case 2'};
  
  legend(fn,'Location','NorthWest');
  </code></pre>