It should be possible to pipe to file and then fire off a subprocess to open the resulting png.
In Windows, you can do:
os.system("start {}".format(output_file_name))
to open the output file with the default Windows program to view that file type (although if there is no registered program to open files of that extension, you'll get the usual prompt asking you what program you want to use to open the file.
Similarly, you can use `open` in OS X and `gnome-open` in at least some flavors of Linux (including Ubuntu).
Of course, you could always allow this command to be user configurable, with the defaults above depending on the OS in which the code is running.
