Discrepancy between Python and Guile wrt exiting the interpreter

[Eli Zaretskii <eliz at gnu dot org>]

If you invoke the Guile interpreter from GDB:

  (gdb) gr

then typing ,q followed by Enter exits the Guile interpreter back to
GDB.  However, if the Python interpreter is started:

  (gdb) pi

then typing quit() and Enter exits GDB, not just the Python
interpreter.  Why do these two interpreters behave differently in this
context?  Is there some other Python command to exit the interpreter?
(I know about Ctrl-D, but I'm asking about commands.)

Thanks.