You probably mean the POSIX shell [1] ;) I never understood why folks venture into bashisms for no or little gain (bash isn't even the default shell on Debian/Devuan), or would invent/use entire new languages with singleton implementations such as Perl in the 1990s or Python in the 2000s (other than for fun, of course).
Note that Python is actually a descendant of the ABC programming language developed to be human-friendly, not a shell replacement language per se.
No, I don't "probably" mean POSIX, if I write Bourne and Korn shell, then that is what I mean! I grew up on real UNIX operating systems, not the GNU/Linux cheap knockoff! Boy do statements like these make me furious!
I have nothing at all against POSIX, but unless one is running HP-UX, Solaris or an illumos-based OS like SmartOS, POSIX compliance is spotty at best in other operating systems.
For this reason, the safest thing to do is write code for either the original Bourne shell, or ksh. Programs written in ksh are the most portable across systems, moreso since other systems have it too. And to top it all off, ksh sets the standard for POSIX, especially ksh93.
Note that Python is actually a descendant of the ABC programming language developed to be human-friendly, not a shell replacement language per se.
[1] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...