Why when use sys.platform on Mac os it print “darwin”?

Question

In Python, when I type sys.platform on the Mac OS X the output is \"darwin\"? Why is this so?

Answer 1

To expand on the other answers: Darwin is the part of OS X that is the actual operating system, in a stricter sense of that term.

To give an analogy, Darwin would be the equivalent of Linux - or Linux and the GNU utilities - while Mac OS X would be the equivalent of Ubuntu or another distribution. I.e. a kernel, the basic userspace utilities, and a GUI layer and a bunch of "built-in" applications.