How can I use Tkinter to visualise time-series data?

I am trying to use Tkinter to visualise some time-series data. My data is in the form of a 2D matrix, with rows referring to blocks and columns referring to a certain period in time. All of the values are between 0 and 1.

I want to create a python script using Tkinter that creates a window, displays the blocks in a square matrix with the first column determining the luminance of each block, then after a predetermined amount of time, change the luminance of the blocks according to successive columns in the data.

I have created a cut-down version of what i have so far:

#!/usr/bin/python

import sys
import os.path
import Tkinter as tk
import math

# program constants
WINDOW_WIDTH = 900

# function to change the colours of the blocks based on current period
def redrawPeriod(t):
    for b in xrange(len(blocks)):
        luminance = int(blocks[b][t] * 255)
        colour = "#%x%x%x" % (luminance,luminance,luminance)
        canvas.itemconfig(block_ids[b],fill=colour)

# sample data (4 blocks 4 periods)
blocks = [
        [0.0, 0.2, 0.5, 0.8],
        [0.3, 0.0, 0.4, 0.0],
        [0.5, 0.7, 0.0, 1.0],
        [0.0, 0.0, 0.3, 0.6],
        [1.0, 0.5, 0.2, 0.9]
      ]

# get number of blocks and periods
nB = len(blocks)
nT = len(blocks[0])

n_cols = int(math.sqrt(nB))
n_rows = n_cols

# if not perfect square number of blocks, add extra row
if (nB % n_rows != 0):
    n_rows = n_rows + 1

# calculate block size
BLOCK_SIZE = WINDOW_WIDTH / n_cols
WINDOW_HEIGHT = BLOCK_SIZE * n_rows

# initialise Tkinter
root = tk.Tk()

# initialise canvas
canvas = tk.Canvas(root, width=WINDOW_WIDTH, height=WINDOW_HEIGHT, background="#002080")

# open canvas
canvas.pack()

# container for block objects
block_ids = []

x = 0
y = -1*BLOCK_SIZE

# initialise block objects
for b in xrange(nB):
    if (b % n_cols == 0):
        x = 0
        y = y + BLOCK_SIZE

    luminance = int(blocks[b][0] * 255)
    colour = "#%x%x%x" % (luminance,luminance,luminance)
    id = canvas.create_rectangle(x, y, x+BLOCK_SIZE, y+BLOCK_SIZE, outline="",fill = colour)
    block_ids.append(id)
    x = x + BLOCK_SIZE

for t in xrange(nT):
    root.after(1000, redrawPeriod,t)

root.mainloop()

This seems to do what i want it to, however it skips straight to the final frame every time - ie. it doesn't draw one frame, pause, draw another frame, pause again, etc.

Can anyone please help me work out what I am doing wrong?