Plotting in a non-blocking way with Matplotlib

I have been playing with Numpy and matplotlib in the last few days. I am having problems trying to make matplotlib plot a function without blocking execution. I know there are already many threads here on SO asking similar questions, and I ‘ve googled quite a lot but haven’t managed to make this work.

I have tried using show(block=False) as some people suggest, but all I get is a frozen window. If I simply call show(), the result is plotted properly but execution is blocked until the window is closed. From other threads I ‘ve read, I suspect that whether show(block=False) works or not depends on the backend. Is this correct? My back end is Qt4Agg. Could you have a look at my code and tell me if you see something wrong? Here is my code. Thanks for any help.

from math import *
from matplotlib import pyplot as plt
print(plt.get_backend())



def main():
    x = range(-50, 51, 1)
    for pow in range(1,5):   # plot x^1, x^2, ..., x^4

        y = [Xi**pow for Xi in x]
        print(y)

        plt.plot(x, y)
        plt.draw()
        #plt.show()             #this plots correctly, but blocks execution.
        plt.show(block=False)   #this creates an empty frozen window.
        _ = raw_input("Press [enter] to continue.")


if __name__ == '__main__':
    main()

PS. I forgot to say that I would like to update the existing window every time I plot something, instead of creating a new one.