What is the use of the wx.App class (apart from what the documentation says), when you can just create a frame and .Show(True) it?
When should a wx.App class be used, or why shouldn't you create a frame and just show it?
The wx.App does a bunch of behind the scenes stuff to make your application work. It does the main loop, which is what waits for the user to do something and then responds. You have to have it. As FogleBird mentioned. By the way, you should NOT have more than one. Doing so will cause weird issues, if it works at all.
purpose of wx.App when just showing a frame is enough