# Boolean Polynomial Ring

Dear all, I am working polynomial ring of 100 binary variables. Sometime I get polynomial with only 4 variables. I want to study these polynomials. My following code is giving error:

```
from sage.crypto.boolean_function import BooleanFunction
V = BooleanPolynomialRing(100,['x%d'%(i) for i in range(100)])
V.inject_variables()
f=x1*x2+x3*x4
xx=f.variables()
l=len(xx)
P=BooleanPolynomialRing(l,map(str,xx))
f=P(f)
```