I'm planning to write a small GUI around a numerical simulation which is why I'm now playing around with Tkinter. Simulations should be launched from GUI in seperate processes. To play around a bit I defined a function random_process that generates pairs of randn numbers (this should later be a real simulation process). As that function is meant to be launched in a seperate process, two mp.Event objects and one mp.Pipe object are passed as parameters. The main application can use one event to request accumulated data from the process, another event is used as a "Poison Pill" to kill the "simulation" process. A pipe is then used to pass the data. In the main application, I use Tkinter's after-function to regularly check if new data has arrived and then plot it. Starting and stopping the "simulation process" is done by buttons in the main app, the same goes for requesting data from it.
At least that was the idea, in practice the program doesn't play nice. When I click on the "go!" button that is meant to launch the simulation process, a second Tkinter window appears, identical to the main one. I don't have the slightest clue why that happens. The communication with the process doesn't work neither, no data seems to be send. When googling for a solution, I found a working example of a Tkinter program launching processes and talking to them, but I didn't find out what makes it not work in my case. Has anybody got a clue?
BTW, the OS is Windows-7.
Cheers, Jan
import matplotlib
matplotlib.use('TkAgg')
import time
import multiprocessing as mp
import Tkinter as Tk
import numpy.random as npr
import matplotlib.figure
import matplotlib.backends.backend_tkagg as tkagg
def random_process(delay, data_request, data_in, poison):
while not poison.is_set():
time.sleep(delay)
print("Generating pair of random numbers...")
x,y = npr.randn(), npr.randn()
try:
random_process.l.append((x,y))
except:
random_process.l = [(x,y)]
if data_request.is_set():
data_request.clear()
try:
ll = len(random_process.l)
if ll > 0:
print("Sending %d pairs to main program.." % ll)
data_in.send(random_process.l)
random_process.l = []
except:
print("data requested, but none there.")
# when poison event is set, clear it:
poison.clear()
class GuiInterfaceApp:
def __init__(self, parent):
self.myParent = parent
self.previewplot_container = Tk.Frame(self.myParent)
self.f = matplotlib.figure.Figure()
self.ax = self.f.add_subplot(111)
self.preview_canvas = tkagg.FigureCanvasTkAgg(self.f, master=self.previewplot_container)
self.preview_canvas.show()
self.button_container = Tk.Frame(self.myParent)
self.hellobutton = Tk.Button(self.button_container, text="hello!")
self.hellobutton.config(command = self.printhello)
self.startbutton = Tk.Button(self.button_container, text="go!")
self.startbutton.config(command=self.run_simulation)
self.plotbutton = Tk.Button(self.button_container, text="show!")
self.plotbutton.config(command=self.request_data)
self.stopbutton = Tk.Button(self.button_container, text="stop.")
self.stopbutton.config(command=self.stop_simulation)
self.quitbutton = Tk.Button(self.button_container, text="get me outta here!")
self.quitbutton.config(command=self.quit_program)
self.previewplot_container.pack(side = Tk.TOP)
self.preview_canvas.get_tk_widget().pack(side=Tk.TOP, fill=Tk.BOTH, expand=1)
self.button_container.pack(side = Tk.BOTTOM)
self.hellobutton.pack(side = Tk.LEFT)
self.startbutton.pack(side = Tk.LEFT)
self.plotbutton.pack(side = Tk.LEFT)
self.stopbutton.pack(side = Tk.LEFT)
self.quitbutton.pack(side = Tk.LEFT)
self.simulation_running = False
self.datarequest = mp.Event()
self.DataIn, self.DataOut = mp.Pipe()
self.PoisonEvent = mp.Event()
self.p = mp.Process(target = random_process, args=(1.0, self.datarequest, self.DataIn, self.PoisonEvent))
self.l = [] # list of received pairs to plot
self.mytask_time = 100 # delay in ms between calls to self.mytask
def printhello(self):
print("hello!")
def run_simulation(self):
print("startbutton pressed.")
if not self.simulation_running:
print("starting simulation...")
self.p.start()
self.simulation_running = True # attention: no error checking
def stop_simulation(self):
print("stop button pressed.")
if self.simulation_running:
print("Sending poison pill to simulation process..")
self.PoisonEvent.set()
self.simulation_running = False
# todo: wait a short amount of time and check if simu stopped.
def request_data(self):
print("plotbutton pressed.")
if self.simulation_running:
print("requesting data from simulation process")
self.datarequest.set()
def update_plot(self):
print("update_plot called.")
if len(self.l) > 0:
print("there is data to plot.")
while len(self.l) > 0:
x,y = self.l.pop()
print("plotting point (%.2f, %.2f)" % (x,y))
self.ax.plot([x], [y], '.', color='blue')
print("drawing the hole thing..")
self.ax.draw()
else:
print("nothing to draw")
def quit_program(self):
print("quitbutton pressed.")
if self.simulation_running:
print("sending poison pill to simulation process..")
self.PoisonEvent.set()
print("quitting mainloop..")
self.myParent.quit()
print("destroying root window..")
self.myParent.destroy()
def receive_data(self):
if self.DataOut.poll():
print("receiving data..")
data = self.DataOut.recv()
self.l.append(data)
self.update_plot()
def my_tasks(self):
self.receive_data()
self.myParent.after(self.mytask_time, self.my_tasks)
return
root = Tk.Tk()
myGuiInterfaceApp = GuiInterfaceApp(root)
root.after(100, myGuiInterfaceApp.my_tasks)
root.mainloop()
