Defining and accessing the variables outside of loop

Question

I want to define or access the eight variables J1L, J2L, J3L, J4L and J1R, J2R, J3R, J4R outside of loop. To make it clear, here in the code, I am defining these eight quantities inside the loop, is there a way to define them outside? Or, as they are already defined here, how can I use them outside the loop. Here is the relevant part of the code:

import numpy as np

def sweep():
    num_cells = 10
    phi = np.ones(num_cells)
    psi = np.zeros((num_cells + 1, 4))
    cur = np.ones(num_cells)
    mu = np.array([-0.8611363115, -0.3399810435, 0.3399810435, 0.8611363115])
    w = np.array([0.3478548451, 0.6521451549, 0.6521451549, 0.3478548451])
    tolerance = 1e-6
    max_it = 100
    err_phi = 1
    it = 0
    A = np.zeros((num_cells, 4))
    B = np.zeros((num_cells, 4))
    S = np.ones((num_cells, 4)) * 0.5
    Q = np.copy(S)
    L = 10.0
    sigma_s = 1.0
    sigma_t = 2.0
    dx = L / num_cells

for i in range(0, num_cells):
    for n in range(0, 4):
        smu = np.sign(mu[n])
        denom = 2.0 * mu[n] + smu * sigma_t * dx
        A[i, n] = (2.0 * mu[n] - smu * sigma_t * dx) / denom
        B[i, n] = smu * 2.0 * dx / denom

while err_phi > tolerance and it <= max_it:
    phi_old = np.zeros(num_cells)
    for i in range(num_cells):
        phi_old[i] = phi[i]

    for i in range(num_cells):
        Q[i, :] = S[i, :] + 0.5 * phi[i] * sigma_s

    #Boundary Condition
    for i in range(0, num_cells):
    psi[i, :] = 0.0

    # Right to left
    for i in range(num_cells - 1, -1, -1):
    psi[i, 0:2] = A[i, 0:2] * psi[i + 1, 0:2] + B[i, 0:2] * Q[i, 0:2]
        J1L = psi[9, 0:2] * mu[0:2]        
        J2L = psi[6, 0:2] * mu[0:2] 
        J3L = psi[3, 0:2] * mu[0:2]
        J4L = psi[0, 0:2] * mu[0:2]
        print J1L, J2L, J3L, J4L

    # Left to right
    for i in range(0, num_cells):
        psi[i + 1, 2:4] = A[i, 2:4] * psi[i, 2:4] + B[i, 2:4] * Q[i, 2:4]
        J1R = psi[0, 0:2] * mu[0:2]        
        J2R = psi[3, 0:2] * mu[0:2] 
        J3R = psi[6, 0:2] * mu[0:2]
        J4R = psi[9, 0:2] * mu[0:2]
        print J1L, J2L, J3L, J4L

    # Update phi
    for i in range(num_cells):
        tot = 0.0
        for n in range(0, 4):
            tot = tot + w[n] * 0.5 * (psi[i, n] + psi[i + 1, n])
        phi[i] = tot

    err_phi = np.amax(np.absolute(((phi - phi_old) / phi_old)))
    it = it + 1
    if it <= max_it:
        print(("converged in", it, "iterations"))

return phi

Answer 1

You could define them at the top of your method by setting each variable equal to zero. The values will change in your loops and then at the end of the loop, the values will remain what they were at the end.