HOWTO: Your first wxPython application

Hello World

Every programming language and UI toolkit needs to have a Hello World example. I think it’s the law in most jurisdictions. :thinking: Their intent is obviously to tell you everything you need to know in order to select the language or toolkit for your own use.

So, here is wxPython’s Hello World:

# First things, first. Import the wxPython package.
import wx

# Next, create an application object.
app = wx.App()

# Then a frame.
frm = wx.Frame(None, title="Hello World")

# Show it.
frm.Show()

# Start the event loop.
app.MainLoop()

Just five lines of code to create and show a window, and run an event handler. That’s really all it takes.

What, you think 5 lines is too many? Okay, fine. Here it is in one line :stuck_out_tongue_winking_eye: :

import wx; a=wx.App(); wx.Frame(None, title="Hello World").Show(); a.MainLoop()

Hello World, Part 2

Okay, now let’s put a little more flesh on the bones of that Hello World sample to give a little better idea of what creating a wxPython application is all about. The finished application looks like these screenshots when run:

HelloWorld2-msw

HelloWorld2-osx

And here is the source code. The docstrings and the comments in the code will help you understand what it is doing.

#!/bin/python
"""
Hello World, but with more meat.
"""

import wx

class HelloFrame(wx.Frame):
    """
    A Frame that says Hello World
    """

    def __init__(self, *args, **kw):
        # ensure the parent's __init__ is called
        super(HelloFrame, self).__init__(*args, **kw)

        # create a panel in the frame
        pnl = wx.Panel(self)

        # put some text with a larger bold font on it
        st = wx.StaticText(pnl, label="Hello World!")
        font = st.GetFont()
        font.PointSize += 10
        font = font.Bold()
        st.SetFont(font)

        # and create a sizer to manage the layout of child widgets
        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(st, wx.SizerFlags().Border(wx.TOP|wx.LEFT, 25))
        pnl.SetSizer(sizer)

        # create a menu bar
        self.makeMenuBar()

        # and a status bar
        self.CreateStatusBar()
        self.SetStatusText("Welcome to wxPython!")

    def makeMenuBar(self):
        """
        A menu bar is composed of menus, which are composed of menu items.
        This method builds a set of menus and binds handlers to be called
        when the menu item is selected.
        """
        
        # Make a file menu with Hello and Exit items
        fileMenu = wx.Menu()
        # The "\t..." syntax defines an accelerator key that also triggers
        # the same event
        helloItem = fileMenu.Append(-1, "&Hello...\tCtrl-H", 
                "Help string shown in status bar for this menu item")
        fileMenu.AppendSeparator()
        # When using a stock ID we don't need to specify the menu item's
        # label
        exitItem = fileMenu.Append(wx.ID_EXIT)

        # Now a help menu for the about item
        helpMenu = wx.Menu()
        aboutItem = helpMenu.Append(wx.ID_ABOUT)

        # Make the menu bar and add the two menus to it. The '&' defines
        # that the next letter is the "mnemonic" for the menu item. On the
        # platforms that support it those letters are underlined and can be
        # triggered from the keyboard.
        menuBar = wx.MenuBar()
        menuBar.Append(fileMenu, "&File")
        menuBar.Append(helpMenu, "&Help")

        # Give the menu bar to the frame
        self.SetMenuBar(menuBar)

        # Finally, associate a handler function with the EVT_MENU event for
        # each of the menu items. That means that when that menu item is
        # activated then the associated handler function will be called.
        self.Bind(wx.EVT_MENU, self.OnHello, helloItem)
        self.Bind(wx.EVT_MENU, self.OnExit,  exitItem)
        self.Bind(wx.EVT_MENU, self.OnAbout, aboutItem)

    def OnExit(self, event):
        """Close the frame, terminating the application."""
        self.Close(True)

    def OnHello(self, event):
        """Say hello to the user."""
        wx.MessageBox("Hello again from wxPython")

    def OnAbout(self, event):
        """Display an About Dialog"""
        wx.MessageBox("This is a wxPython Hello World sample", 
                      "About Hello World 2",
                      wx.OK|wx.ICON_INFORMATION)

if __name__ == '__main__':
    # When this module is run (not imported) then create the app, the
    # frame, show it, and start the event loop.
    app = wx.App()
    frm = HelloFrame(None, title='Hello World 2')
    frm.Show()
    app.MainLoop()