Polynomial Ring in Sage

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Hello, I want to use this code in my python script, but it return error:

from sage.all import *
var('x')
R = ZZ['x']
f = 3*x**2 - 3*x**8
g = x**2 - 1
print g.degree(x)
h = f.mod(x**2 - 1)
print h.degree(x)
print f.quo_rem(g)

and error:

2
8
Traceback (most recent call last):
  File "degree.py", line 15, in <module>
    print f.quo_rem(g)
  File "sage/structure/element.pyx", line 438, in sage.structure.element.Element.__getattr__ (build/cythonized/sage/structure/element.c:4406)
  File "sage/structure/misc.pyx", line 257, in sage.structure.misc.getattr_from_other_class (build/cythonized/sage/structure/misc.c:1631)
AttributeError: 'sage.symbolic.expression.Expression' object has no attribute 'quo_rem'

What's the problem I can't use this commands in my script? And also note the the result of

h = f.mod(x**2 - 1)