Ah, Stackoverflow had the answer:

    import platform<br></br>
    platform.system()<br></br><br></br>

That gives me 'Linux' when I run python natively, and 'Windows' under Wine. I don't know what the value will be on Macs, supposedly something like 'Macos' or 'MacOS'.

-- I'm not mad at you, just Westphalian.