# Set global RealNumber precision in .sage file

I want to change the real number precision from 53 to, say, 100.

I found this very similar question: ask.sagemath.org/question/7887/set-global-precision-for-reals/ (sorry it doesn't let me post a link), which says to use
`R=RealField(100); RealNumber=R`

I tried it and it only works for me in the sage commandline, but not in .sage programs. Why is that and how do I get around it?