Rotation generator

from numpy import cos, sin, array
from math import pi

# polar angle (down from z-axis)
theta = pi/2
# azimuthal angle (off the x axis)
phi = pi/2

# step 1: to get the desired theta, rotate about the y-axis by theta (not sure if this is exactly what the want. if not, just use Rx)
Ry = array([
    [cos(theta), 0, sin(theta)],
    [0, 1, 0],
    [-sin(theta), 0, cos(theta)]
])
# Rx = array([
#     [1, 0, 0],
#     [0, cos(theta), -sin(theta)],
#     [0, sin(theta), cos(theta)]
# ]).T

# step 2: to get the desired phi, rotate about the z-axis by phi
Rz = array([
    [cos(phi), -sin(phi), 0],
    [sin(phi), cos(phi), 0],
    [0, 0, 1],
])

# start with a vector along the positive z direction
vec = array([0,0,1])

print(Rz.dot(Ry.dot(vec)))