I wrote an app to plot a graph from an input file when you drag and drop the file onto a gui interface. However after the execution of plt.show() in the program, the gui interface becomes inactve. 
Using plt.draw() instead of plt.show() or using plt.ion() solves this issue, but then the python graph stop updating, ie. resizing/ closing the graph doesn't work until the next time a file is dragged and dropped.
Try to make two different files and put the plt.show() in the other one, to see if it works.
plt.show() stops gui interface from updating