Matplotlib show/draw works only once

[Daniel M]

I am writing a GUI program in Tkinter which allows the user to enter in different parameters specifying an ellipse segment. Then, he/she presses a button and the ellipse segment is plotted, using matplotlib. Here is the code (inside a class, but logically stands alone) that does this:

aa = DataArray(self.file0)  #Retrieve data sets
bb = DataArray(self.file1)  #Not used right now
cc = DataArray(self.file2)  #Not used right now
curr = DataArray(self.file3)#Not used right now
            
x = aa.x                 #Get the abcissa values from the initial data set
            
ideal = IdealEllipse(float(self.r.get()) , float(self.r.get()), float(self.r.get()),xall)

plt1 = plt.plot(x,ideal)

plt.draw()

It works the first time, but if the user closes the window and then tries to plot it again, only a blank graph shows up. I have tried using pyplot.show(), and I get the same result. Even if I insert pyplot.close() at the top, to close all figures, it still does not change this. Using the figure manager and interactive mode also do not change this result. I have searched through the documentation and message boards all over the place but cannot find an explanation for this. I have the most up-to-date version of matplotlib (for Python 2.6). Why is this happening?

Thanks in advance for any help

[dwblas]

What is self.r.get() and why do you call the function 3 times instead of calling it once and storing the value?

It works the first time, but if the user closes the window and then tries to plot it again, only a blank graph shows up

I'm guessing that r.get() doesn't exist once the window is closed but we can't tell from the code you posted. Storing r.get() in a variable would make the value persistent when the variable still exists after the window is closed.

[Daniel M]

This is all inside the command function for a button. I don't close the GUI, I just close the plot window. And then when I try to bring it back up by pressing the button, I get a blank graph. The repeated r.get() calls is a mistake. The whole function (as I am currently testing it) is:

def ParOpt(self):
        Ready = (self.r.get() != '') and (self.rp.get() != '') and (self.th.get() != '')
        Ready = Ready and (self.Chg1.get()!= '') and (self.Chg2.get()!= '')
        Ready = Ready and (self.Name0.get() != '') and (self.Name1.get() != '')
        Ready = Ready and (self.Name2.get() != '') and (self.Name3.get() != '')
        
        if Ready == 1:

            plt.ion()
            aa = DataArray(self.file0)  #Retrieve data sets
            bb = DataArray(self.file1)
            cc = DataArray(self.file2)
            curr = DataArray(self.file3)            

            d1 = float32(self.Chg1.get())
            d2 = float32(self.Chg2.get())
            
            xall = aa.x                 #Get the abcissa values from the initial data set
            
            ideal = IdealEllipse(float(self.r.get()) , float(self.rp.get()), float(self.th.get()),xall)

            Solution = Optimize(ideal,aa.s,bb.s,cc.s,d1,d2,curr.s)

            s1 = str( SigFig(sqrt(Solution.disp[0,0]),sqrt(Solution.disp[0,0])) )
            s2 = str( SigFig(sqrt(Solution.disp[1,1]),sqrt(Solution.disp[1,1])) )

            # See if answer is already open
            try:
                answer
            except NameError:
                answer = None

            # Test whether variable is defined to be None
            if answer is not None:
                answer.destroy()
                
            answer = Toplevel()
            answer.title("Optimal Parameter Settings")
            
            aL = Label(answer, text = "Change Bender #1 by "+str(SigFig(Solution.sol[0],float(s1)))+" (+/-"+s1+")",width = 50)
            aL.pack()
            
            aL = Label(answer, text = "Change Bender #2 by "+str(SigFig(Solution.sol[1],float(s2)))+" (+/-"+s2+")",width = 50)
            aL.pack()

            nd = [self.r.get()+'\t'+self.rp.get()+'\t'+self.th.get()+'\t'+str(d1)+'\t'+str(d2)+'\t'+'END\n']
            nd.append(self.Name0.get()+'\t\n')
            nd.append(self.Name1.get()+'\t\n')
            nd.append(self.Name2.get()+'\t\n')
            nd.append(self.Name3.get()+'\t\n')
                       
            newDefaults = open('C:\Documents and Settings\dmerthe\Desktop\Merthe Ellipse Adjust Test Files\defaultvalues.txt','w')
            newDefaults.writelines(nd)

            newDefaults.close()

            DiffInit = curr.s - ideal - mean(curr.s - ideal)
            DiffFin = Solution.pred - ideal - mean(Solution.pred - ideal)

            cf1 = (bb.s - aa.s)/d1
            cf2 = (cc.s - bb.s)/d2

            plt1 = plt.plot(xall,DiffInit,'b',xall,DiffFin,'r--')

            xRange = max(xall) - min(xall)
            ymin1 = min(DiffInit)
            ymax1 = max(DiffInit)
            ymin2 = min(DiffFin)
            ymax2 = max(DiffFin)
            ymax = max([ymax1,ymax2])
            yrange = max([ymax1,ymax2]) - min([ymin1,ymin2])

            sInit = SigFig(std(DiffInit),std(DiffInit)*1.0E-2)
            sFin = SigFig(std(DiffFin),std(DiffFin)*1.0E-2)

            txt1 = plt.text(min(xall)+0.1*xRange, ymax, 'Current State, $\sigma = $'+str(sInit*1.0E6)+ ' $\mu$rad', color = 'blue', fontsize = 14)
            txt2 = plt.text(min(xall)+0.1*xRange, ymax - 0.1*yrange, 'Predicted Final State, $\sigma = $'+str(sFin*1.0E6)+ ' $\mu$rad', color = 'red', fontsize = 14)

            plt.draw()
            plt.ioff()

[dwblas]

This code accepts a number and plots that number of ellipsis. When the plot window is closed it goes back to the Tkinter entry box to get another number, which you can then plot. Note that you can only do one thing at a time, so when the plot window is open the Tkinter window is not responsive.

try:
    import Tkinter as tk     ## Python 2.x
except ImportError:
    import tkinter as tk     ## Python 3.x

from pylab import figure, show, rand
from matplotlib.patches import Ellipse

class MatPlotTest():
    def __init__(self):
        self.num=1
        self.root = tk.Tk()
        self.create_entry()
        self.root.mainloop()

    def create_entry(self):
        tk.Label(self.root, text="number to create").grid()
        self.entry=tk.Entry(self.root)
        self.entry.grid(row=0, column=1)
        self.entry.focus_set()

        tk.Button(self.root, text="draw ellipsesiess", command=self.plot_it, 
                  bg="lightblue").grid(row=2, column=0)
        tk.Button(self.root, text="Exit", command=self.root.quit, 
                  bg="red").grid(row=2, column=1, sticky="WE")

    def plot_it(self):
        self.num=int(self.entry.get())
        ells = [Ellipse(xy=rand(2)*10, width=rand(), height=rand(), angle=rand()*360)
                for ctr in xrange(self.num)]

        fig = figure()
        self.ax = fig.add_subplot(111, aspect='equal')
        for e in ells:
            self.ax.add_artist(e)
            e.set_clip_box(self.ax.bbox)
            e.set_alpha(rand())
            e.set_facecolor(rand(3))

        self.ax.set_xlim(0, 10)
        self.ax.set_ylim(0, 10)

        show()

MP=MatPlotTest()