circuit_yuan.py

from numpy import array,empty
from numpy.linalg import inv,solve
from numpy import copy,dot



A = array([[1, 1, -1],
           [6, 0, 0],
           [0, 0, 9]], float)
v = array([0,6,12],float)
N = len(v)


B=copy(A)
vold=copy(v)



# Gaussian elimination
for m in range(N):

    # Divide by the diagonal element
    div = A[m,m]
    A[m,:] /= div
    v[m] /= div

    # Now subtract from the lower rows
    for i in range(m+1,N):
        mult = A[i,m]
        A[i,:] -= mult*A[m,:]
        v[i] -= mult*v[m]

# Backsubstitution
x = empty(N,float)
for m in range(N-1,-1,-1):
    x[m] = v[m]
    for i in range(m+1,N):
        x[m] -= A[m,i]*x[i]

print(x)