Not quite working tomo recon from images

tomo.py

from PIL import Image
import matplotlib.pyplot as plt
import numpy as np

from skimage.io import imread
from skimage.transform import radon, iradon
from scipy.ndimage import zoom

basename = "projection_"
extention = ".jpeg"
plt.figure(figsize=(15, 15.5))
plt.subplot(221)

projections = 0
cs_array = [[]]

for x in range(0, 50):
    name = basename + str(x).zfill(4) + extention
    print name
    image = imread(name, as_grey=True)
    image_data = np.asarray(image)
    cs_array[x] = image_data[120]
    
#plt.plot(projections);
cs = Image.fromarray(cs_array)
plt.imshow(cs, cmap=plt.cm.Greys_r)

# gives this error

#  File "tomo.py", line 30, in <module>
#    cs_array[x] = image_data[120]

#IndexError: list assignment index out of range

Maybe print x at line 22? Maybe adjust the loop for one image only and read the image data into another type of variable to see if it’s a problem with passing to the array?