wxPython: execute command asynchronously, display stdout in text widget

Question

I'm looking for the wxPython equivalent to my answer for Tcl/Tk examples?. Specifically, I want to see an example of how to create several buttons, each of which runs some external command when clicked. While the process is running I want the output to go to a scrollable wxPython widget.

While the process is running the GUI should not block. Assume, for example, one of the buttons may kick off a development task like building or running unit tests.

Answer 1

Start a thread when a button is clicked:

try:
    r = threading.Thread(target=self.mycallback)
    r.setDaemon(1)
    r.start()
except:
    print "Error starting thread"
    return False

Use wx.PostEvent and wx.lib.newevent to send messages from the callbacks to the main thread.

This link may be helpful.

Answer 2

Bryan, try something like this:

import subprocess, sys

def doit(cmd):
    #print cmd
    out = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True).stdout
    return out.read()

So when the button is pressed, the command gets run using the subprocess module, and you get the output as a string. You can assign it to a Text Control's value to show it. You might have to out.readfully() or read multiple times to show text progressively.

If the button & text field aren't familiar, then a quick look at the wxPython demo will show you exactly what to do.

Answer 3

Here you are, a complete working example.

import wx
import functools
import threading
import subprocess
import time

class Frame(wx.Frame):
    def __init__(self):
        super(Frame, self).__init__(None, -1, 'Threading Example')
        # add some buttons and a text control
        panel = wx.Panel(self, -1)
        sizer = wx.BoxSizer(wx.VERTICAL)
        for i in range(3):
            name = 'Button %d' % (i+1)
            button = wx.Button(panel, -1, name)
            func = functools.partial(self.on_button, button=name)
            button.Bind(wx.EVT_BUTTON, func)
            sizer.Add(button, 0, wx.ALL, 5)
        text = wx.TextCtrl(panel, -1, style=wx.TE_MULTILINE|wx.TE_READONLY)
        self.text = text
        sizer.Add(text, 1, wx.EXPAND|wx.ALL, 5)
        panel.SetSizer(sizer)
    def on_button(self, event, button):
        # create a new thread when a button is pressed
        thread = threading.Thread(target=self.run, args=(button,))
        thread.setDaemon(True)
        thread.start()
    def on_text(self, text):
        self.text.AppendText(text)
    def run(self, button):
        cmd = ['ls', '-lta']
        proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
        for line in proc.stdout:
            wx.CallAfter(self.on_text, line)

if __name__ == '__main__':
    app = wx.PySimpleApp()
    frame = Frame()
    frame.Show()
    app.MainLoop()