title: Displaying numbers with "X" instead of "e" scientific notation in matplotlib
body: <p>Using matplotlib, I would like to write text on my plots that displays in normal scientific notation, for example, as 1.92x10<sup>-7</sup> instead of the default 1.92e-7.  I have found help on how to do this for numbers labeling ticks on the axes but not for the text function.  Here is an example of my code that I would like to change:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  x = np.linspace(0,0.5)
  y = x*(1.0-x)
  
  a=1.92e-7
  
  plt.figure()
  plt.plot(x, y)
  plt.text(0.01, 0.23, r"$a = {0:0.2e}$".format(a), size=20)
  plt.show()
  </code></pre>