Pyside 2 example does not work as intended on OS X 10.13.4

Copy and pasting the code from Qt for Python site, under the "Show me the Code" section runs under OS X, but clicking on the button presented does not change the displayed "Hello World" QLabel with a random choice from a list of strings. I've tried the other tutorials and they all worked as intended, so I'm not sure what is happening. I tried adding a small print debug line (print("Caught signal!") as the first line of the magic() method, and it does print out to the console.