#!/usr/bin/env python
# -*- coding: utf-8 -*-

import os, serial, wx
from serial.tools import list_ports

class COMPort:
    def __init__(self, id, name):
        self.id = id
        self.name = name

class COMPortSelectForm(wx.Frame):
    def __init__(self):
        # Create non-resizable frame
        wx.Frame.__init__(self, None, title="Select Arduino COM port", style=wx.DEFAULT_FRAME_STYLE^wx.RESIZE_BORDER, size=(200, 135))
        self.Centre()
        panel = wx.Panel(self, wx.ID_ANY)

        # Create a drop down menu with all available COM ports
        comPortChoices = []
        combobox = wx.ComboBox(panel, size=wx.DefaultSize, choices=comPortChoices, style=wx.CB_READONLY)
        self.combobox = combobox
        for comport in list_serial_ports():
            combobox.Append(comport.name, comport)
        combobox.SetSelection(0)

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(wx.StaticText(panel, label="Select Arduino COM port"), flag=wx.LEFT|wx.RIGHT|wx.TOP|wx.ALIGN_CENTER_HORIZONTAL, border=10)
        sizer.Add(combobox, 0, flag=wx.LEFT|wx.RIGHT|wx.TOP|wx.EXPAND, border=10)
        selectButton = wx.Button(panel, label="Select", size=(-1, 30))
        sizer.Add(selectButton, 0, flag=wx.ALL|wx.EXPAND, border=10)
        selectButton.Bind(wx.EVT_BUTTON, self.onClick)
        panel.SetSizer(sizer)

    def onClick(self, event):
        print "You selected: " + self.combobox.GetStringSelection()

# Source: http://stackoverflow.com/a/14224477
def list_serial_ports():
    # Windows
    if os.name == "nt":
        # Scan for available ports
        available = []
        for i in range(256):
            try:
                s = serial.Serial(i)
                available.append(COMPort(i, "COM"+str(i + 1)))
                s.close()
            except serial.SerialException:
                pass
        return available
    else:
        # Mac / Linux
        return [COMPort(port[0], port[0]) for port in list_ports.comports()]

if __name__ == "__main__":
    app = wx.App(False)
    frame = COMPortSelectForm()
    frame.Show()
    app.MainLoop()

Create COM port selection GUI.
Create COM port selection GUI.
