while True:

studRegistered $=$ int$($input$("$Are you registering for Python $101?($Maximum $21$ students$)$: $"))$

if $1<=$ studRegistered $<=21$:

print$($f$"$Successfully registered $\{$studRegistered$\}$ student!"$)$

break #once input was received

else:

print$("$Students registered must be between $1$ and $21.$ Please re$-$enter: $")$

Can you explain this range operator if $1<=$ studRegistered $<=21$:

Why can't $(1,21)$ be used?