title: read and plot multiple txt files in python
body: <p>I have some output files ie frequency1 .txt , frequency2 .txt and so on (till 21). In each txt files I am having 10 columns and suppose n rows , now I need to plot column 2 and column 3 for all these txt files .I am able to plot for a single txt file </p>
  
  <pre><code>import numpy as np
  from matplotlib import pyplot as plt
  
  data=np.loadtxt('frequecy1.txt')
  pl.plot(data[:,1],data[:,2],'bo')
  X=data[:,1]
  Y=data[:,2]
  plt.plot(X,Y,':ro')
  plt.ylim((0,55000))
  plt.show()
  </code></pre>
  
  <p>How would I plot all the files?</p>