Handle plot with Tkinter

Question

I want to handle a plot window with some Tkinter buttons. Like for example plot matrix columns and switch columns with buttons. I ve tried this :

import numpy
import pylab
import Tkinter

pylab.ion()
# Functions definitions:
x = numpy.arange(0.0,3.0,0.01)
y = numpy.sin(2*numpy.pi*x)
Y = numpy.vstack((y,y/2,y/3,y/4))

#Usual plot depending on a parameter n:
def graphic_plot(n):
    if n < 0: n = 0
    if n > len(Y): n = len(Y)-1
    fig = pylab.figure(figsize=(8,5))
    ax = fig.add_subplot(111)
    ax.plot(x,Y[n,:],'x',markersize=2)
    ax.set_xlabel('x title')
    ax.set_ylabel('y title')
    ax.set_xlim(0.0,3.0)
    ax.set_ylim(-1.0,1.0)
    ax.grid(True)
    pylab.show()


def increase(n):
   return n+1

def decrease(n):
    return n-1

n=0
master = Tkinter.Tk()
left_button  = Tkinter.Button(master,text="<",command=decrease(n))
left_button.pack(side="left")
right_button = Tkinter.Button(master,text=">",command=increase(n))
right_button.pack(side="left")
master.mainloop()

But I dont't know when to call the graphic_plot function and refresh the graphic correspondingly to the nparameter.

Matt Fenwick · Accepted Answer · 2012-04-04 12:34:35Z

First off, you need to pass a function to the command parameter in buttons. In this code,

left_button  = Tkinter.Button(master, text="<", command=decrease(n))

you're handing decrease(0), or -1, to command.

Other problems:

we can't just pass in decrease because it takes a parameter
n's state is never changed
the plot should be updated whenever n is inced/deced

We can easily solve these problems by moving n into a class with a couple of methods:

class SimpleModel:

  def __init__(self):
    self.n = 0

  def increment(self):
    self.n += 1
    graphic_plot(self.n)

  def decrement(self):
    self.n -= 1
    graphic_plot(self.n)

Then for the buttons, we'll have:

model = SimpleModel()  # create a model

left_button  = Tkinter.Button(master, text="<", command=model.decrease)

right_button = Tkinter.Button(master, text=">", command=model.increase)

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