Unlike Perl or Tcl, Python is not just a scripting language with a set of ad-hoc extensions. There are still issues, and Python probably will never be a general-purpose replacement for system-native language compilers, but it does enable a smooth ramp from "just a user," through "a user who does some scripting," to "application developer."
I'd really like to know which features of Python move the language out of the "just a scripting language" ghetto into the idyllic Elysian Fields of Real System Programming For Real God-like Men, 'cuz enforced indentation just ain't it.
(I'll accept the answer of ctypes, but be aware that it's just as much an ad-hoc extension as any other externally-developed feature eventually borged into the standard library. It's still something Perl should borrow from Python.)