title: Updating PyQt progressbar based on printed stdout from imported package (PyQt5)
body: <p>I'm relatively new to PyQt5 and would appreciate any guidance in achieving the following please.</p>
  
  <p>I'm building a GUI to work on top of a Python package that runs various slow processing tools. The current interface is purely textual: the package runs some code in a loop and prints the current progress percentage completion to the terminal.</p>
  
  <p>My aim is to build a PyQt GUI that displays this progress as a progressbar instead. This could be done simply using QProgressBar.setValue() if I could add this call to the original processing code, but this is not possible; instead, my GUI is to be built on top of the current text output interface from the processing code.</p>
  
  <p>I feel like this should be possible using a thread somehow, but am not sure how to intercept the call to stdout without impeding performance / introducing thread-unsafe operations. </p>
  
  <p>Is this possible? Any suggestions would be great thanks.</p>