Newton forward interpolation

#Newton forward interpolation
from numpy import*

def fact(n):
    if n<=1:
        return(1)
    else:
        return(n*fact(n-1))
       
n=input("Enter no of elements ")
y=zeros([n,n])
x0,h=input("Enter the value of x[0] and finite difference ")
x=[x0+i*h for i in range(n)]

print "Enter y values"
for i in range(n):
    print "Enter y value for x[%d]"%(i)
    y[i,0]=input()
for i in range(1,n):
    k=n-i
    for j in range(k):
        y[j,i]=y[j+1,i-1]-y[j,i-1]
   
print y

xp=input(" Enter the x value for which y is to be found")
u=(xp-x[0])/float(h)
#print "u=",u
yp=y[0,0]
for i in range(1,n):
    t=1
    for j in range(i):
        t=t*(u-j)
    yp=yp+t*y[0,i]/fact(i)
   
print "The value of y is  %f "%(yp)