There Are Multiple Wardens In The Novella
One distinction between Stephen King’s novella and the film is the presence of various wardens during Andy’s term in prison. This explains why Warden Norton’s demeanor and attitude appear to shift so quickly on several times. The warden who is friendly to Andy and lets him send letters and work on the library is not the same as the warden who punishes Andy severely near the end. To make things easier, they combined the several characters into a single individual.

There Are Multiple Wardens In The Novella