title: How to select area within a plot (Python) and extract the data within the area
body: <p>I am currently working with a dataset that includes signals with a duration of around 10 seconds and a sampling time of 0.1 seconds.
  My goal is to extract a specific part of this data and save it into a python dictionary. The relevant part is about 4 seconds long.</p>
  
  <p>Ideally this is what I would like to do:</p>
  
  <ol>
  <li><p>Plot the whole 10 seconds of data.</p></li>
  <li><p>Mark the relevant part of the signals for example with a bounding box.</p></li>
  <li><p>Extract the data within the bounding box after closing the plot window or pushing a button.</p></li>
  <li><p>Go back to 1. and take new data.</p></li>
  </ol>
  
  <p>I saw that matplotlib has the ability to draw patches and extract the data points within the patch. Is it maybe possible to add a patch to the plot after the plot was created (after the plt.show() command was executed)?</p>
  
  <p>Thank you in advance and best regards,</p>
  
  <p>Manuel</p>