How can I run the current file in PyCharm? I would like a single hotkey that will execute the current file (whether normal file, scratch file, or scratch buffer) using the project default python interpreter. I would like to NOT have to create a custom run configuration, but just launch with the default Python configuration. Is such a thing possible?

As it turns out, the action I was seeking is "Run context configuration" (or "Debug context configuration" for debugging). The default key binding on Windows is ctrl+shift+f10, or ctrl+option+R on Mac, as Ev. Kounis pointed out, although you can bind it to any key you like.

These settings can be found under the "Other" section in File->Settings->Keymap. The easiest way to find them is to simply use the search box.