Confusion about GUID functionality in GH vs. Python

It seems that GH can handle a list of guids to make a series of sphere or other geometry from the output of my code; however, if I try and add the spheres inside the python code, this will not work. I believe i need to coerce the points somehow in python, but I'm not sure. 

I always run into this error. What am I missing?

import rhinoscriptsyntax as rs
import perlin

sn = perlin.SimplexNoise()

pList = []

for i in range(x):
for j in range(y):
for k in range(z):
perVal = sn.noise3(i*scaleX, j*scaleY, k*scaleZ)

if (perVal > lowLim and perVal < upperLim):
point = rs.AddPoint(i,j,k)
pList.append(point)

a = pList

rs.AddSphere([pList], .25) # here is the issue

print pList