How to update matplotlib plot in while loop?

Asked Oct 13 '14 at 12:35

Active Oct 13 '14 at 12:35

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I am trying to write a script that plots a figure and asks the user to select two points. It then draws a rectangle of which the points are the bottom left and top right corner. The process is then repeated adding a new rectangle each iteration. However, I want it to draw the rectangle immediately after the current points are selected but it does not occur till the next set of points are selected. Anyone know how to fix this?

import matplotlib.pylab as plt

x = rand(10,10)
plt.imshow(x)

select = 'y'
while select == 'y':

    select = (raw_input('select points (y or n) ? '))
    a, b = plt.ginput(2)
    plt.vlines(a[0], a[1], b[1], lw=5)
    plt.vlines(b[0], a[1], b[1], lw=5)
    plt.hlines(a[1], a[0], b[0], lw=5)
    plt.hlines(b[1], a[0], b[0], lw=5)
    plt.draw()

asked Oct 13 '14 at 12:35

Dave

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Your code works for me, It draws a rectangle just after the points are selected. – Sainath Motlakunta Oct 13 '14 at 13:31
seems the problem was with the backend and not the code, switching to TkAgg solved the problem. – Dave Oct 13 '14 at 14:48
You need a `plt.pause()` to give the gui a chance to re-draw itself. – tacaswell Oct 13 '14 at 17:04

How to update matplotlib plot in while loop?

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