Best way to get the name of a button that called an event?

Question

In the following code (inspired by this snippet), I use a single event handler buttonClick to change the title of the window. Currently, I need to evaluate if the Id of the event corresponds to the Id of the button. If I decide to add 50 buttons instead of 2, this method could become cumbersome. Is there a better way to do this?

import wx

class MyFrame(wx.Frame):
    def __init__(self):
        wx.Frame.__init__(self, None, wx.ID_ANY, 'wxBitmapButton',
            pos=(300, 150), size=(300, 350))
        self.panel1 = wx.Panel(self, -1)

        self.button1 = wx.Button(self.panel1, id=-1,
            pos=(10, 20), size = (20,20))
        self.button1.Bind(wx.EVT_BUTTON, self.buttonClick)

        self.button2 = wx.Button(self.panel1, id=-1,
            pos=(40, 20), size = (20,20))
        self.button2.Bind(wx.EVT_BUTTON, self.buttonClick)

        self.Show(True)

    def buttonClick(self,event):
        if event.Id == self.button1.Id:
            self.SetTitle("Button 1 clicked")
        elif event.Id == self.button2.Id:
            self.SetTitle("Button 2 clicked")            

application = wx.PySimpleApp()
window = MyFrame()
application.MainLoop()

Answer 1

Keep a dict with keys that are the .Id of the buttons and values that are the button names or whatever, so instead of a long if/elif chain you do a single dict lookup in buttonClick.

Code snippets: in __init__, add creation and update of the dict:

self.panel1 = wx.Panel(self, -1)
self.thebuttons = dict()

self.button1 = wx.Button(self.panel1, id=-1,
    pos=(10, 20), size = (20,20))
self.thebuttons[self.button1.Id] = 'Button 1'
self.button1.Bind(wx.EVT_BUTTON, self.buttonClick)

and so on for 50 buttons (or whatever) [they might be better created in a loop, btw;-)]. So buttonClick becomes:

   def buttonClick(self,event):
       button_name = self.thebuttons.get(event.Id, '?No button?')
       self.setTitle(button_name + ' clicked')

Answer 2

You could create a dictionary of buttons, and do the look based on the id ... something like this:

class MyFrame(wx.Frame):
   def _add_button (self, *args):
      btn = wx.Button (*args)
      btn.Bind (wx.EVT_BUTTON, self.buttonClick)
      self.buttons[btn.id] = btn
   def __init__ (self):
      self.button = dict ()
      self._add_button (self.panel1, id=-1,
        pos=(10, 20), size = (20,20))

    self._add_button = (self.panel1, id=-1,
        pos=(40, 20), size = (20,20))

    self.Show (True)

   def buttonClick(self,event):
      self.SetTitle (self.buttons[event.Id].label)

Answer 3

I ran into a similar problem: I was generating buttons based on user-supplied data, and I needed the buttons to affect another class, so I needed to pass along information about the buttonclick. What I did was explicitly assign button IDs to each button I generated, then stored information about them in a dictionary to lookup later.

I would have thought there would be a prettier way to do this, constructing a custom event passing along more information, but all I've seen is the dictionary-lookup method. Also, I keep around a list of the buttons so I can erase all of them when needed.

Here's a slightly scrubbed code sample of something similar:

self.buttonDefs = {}
self.buttons = []
id_increment = 800
if (row, col) in self.items:
    for ev in self.items[(row, col)]:
        id_increment += 1
        #### Populate a dict with the event information
        self.buttonDefs[id_increment ] = (row, col, ev['user'])
        ####
        tempBtn = wx.Button(self.sidebar, id_increment , "Choose",
                            (0,50+len(self.buttons)*40), (50,20) )
        self.sidebar.Bind(wx.EVT_BUTTON, self.OnShiftClick, tempBtn)
        self.buttons.append(tempBtn)

def OnShiftClick(self, evt):
    ### Lookup the information from the dict
    row, col, user = self.buttonDefs[evt.GetId()]
    self.WriteToCell(row, col, user)
    self.DrawShiftPicker(row, col)

Answer 4

You could give the button a name, and then look at the name in the event handler.

When you make the button

b = wx.Button(self, 10, "Default Button", (20, 20))
b.myname = "default button"
self.Bind(wx.EVT_BUTTON, self.OnClick, b)

When the button is clicked:

def OnClick(self, event):
    name = event.GetEventObject().myname

Answer 5

I recommend that you use different event handlers to handle events from each button. If there is a lot of commonality, you can combine that into a function which returns a function with the specific behavior you want, for instance:

def goingTo(self, where):
    def goingToHandler(event):
        self.SetTitle("I'm going to " + where)
    return goingToHandler

def __init__(self):
    buttonA.Bind(wx.EVT_BUTTON, self.goingTo("work"))
    # clicking will say "I'm going to work"
    buttonB.Bind(wx.EVT_BUTTON, self.goingTo("home"))
    # clicking will say "I'm going to home"

Answer 6

Take advantage of what you can do in a language like Python. You can pass extra arguments to your event callback function, like so.

import functools

def __init__(self):
    # ...
    for i in range(10):
        name = 'Button %d' % i
        button = wx.Button(parent, -1, name)
        func = functools.partial(self.on_button, name=name)
        button.Bind(wx.EVT_BUTTON, func)
    # ...

def on_button(self, event, name):
    print '%s clicked' % name

Of course, the arguments can be anything you want.

Answer 7

I needed to do the same thing to keep track of button-presses . I used a lambda function to bind to the event . That way I could pass in the entire button object to the event handler function to manipulate accordingly.

    class PlatGridderTop(wx.Frame):
        numbuttons = 0
        buttonlist = []


        def create_another_button(self, event): # wxGlade: PlateGridderTop.<event_handler>
                buttoncreator_id = wx.ID_ANY
                butonname = "button" + str(buttoncreator_id)
                PlateGridderTop.numbuttons = PlateGridderTop.numbuttons + 1
                thisbutton_number = PlateGridderTop.numbuttons

                self.buttonname  =  wx.Button(self,buttoncreator_id ,"ChildButton %s" % thisbutton_number )
                self.Bind(wx.EVT_BUTTON,lambda event, buttonpressed=self.buttonname: self.print_button_press(event,buttonpressed),self.buttonname)
                self.buttonlist.append(self.buttonname)
                self.__do_layout()
                print "Clicked plate button %s" % butonname
                event.Skip()
       def print_button_press(self,event,clickerbutton):
               """Just a dummy method that responds to a button press"""
               print "Clicked a created button named %s with wxpython ID %s" % (clickerbutton.GetLabel(),event.GetId())

Disclaimer : This is my first post to stackoverflow