I am learning Python (v 3.7) on a Mac using PyCharm. As I practice using the turtle library, the program runs without error, outputs the correct graphics, but then the graphics screen disappears immediately after the code completes runnning. Adding time.sleep(5) at the end of my program persists it and also shows that the focus changed from PyCharm to a Python program menu (which I can't find or turn on in the hope of keeping running). 
When I use Thonny, the output persists, so I can check my work. How can I make it persist in PyCharm?
A well-structured Python turtle program will end with a call to mainloop() or one of its variants (exitonclick(), done())  This turns control over to the underlying tkinter event handler which will keep your window open, awaiting user events.  Without this, the program simply ends and the window closes.
You don't need time.sleep() nor input("Press Enter to continue...").  Some Python programming environments clash with mainloop() but even those tend to disable it behind the scenes so the same code works everywhere.
How to persist Python turtle graphics screen