Getting started with wxPython

A First Application: "Hello, World"

As is traditional, we are first going to write a Small "Hello, world" application. Here is the code:

   1 #!/usr/bin/env python
   2 import wx
   3 
   4 app = wx.App(False)  # Create a new app, don't redirect stdout/stderr to a window.
   5 frame = wx.Frame(None, wx.ID_ANY, "Hello World") # A Frame is a top-level window.
   6 frame.Show(True)     # Show the frame.
   7 app.MainLoop()

Explanations:

Note: You almost always want to use wx.ID_ANY or another standard ID (v2.8) provided by wxWidgets. You can make your own IDs, but there is no reason to do that.

Run the program and you should see a window like this one:

Windows or Frames?

When people talk about GUIs, they usually speak of windows, menus and icons. Naturally then, you would expect that wx.Window should represent a window on the screen. Unfortunately, this is not the case. A wx.Window is the base class from which all visual elements are derived (buttons, menus, etc) and what we normally think of as a program window is a wx.Frame. This is an unfortunate inconsistency that has led to much confusion for new users.

Building a simple text editor

In this tutorial we are going to build a simple text editor. In the process, we will explore several widgets, and learn about features such as events and callbacks.

First steps

The first step is to make a simple frame with an editable text box inside. A text box is made with the wx.TextCtrl widget. By default, a text box is a single-line field, but the wx.TE_MULTILINE parameter allows you to enter multiple lines of text.

   1 #!/usr/bin/env python
   2 import wx
   3 class MyFrame(wx.Frame):
   4     """ We simply derive a new class of Frame. """
   5     def __init__(self, parent, title):
   6         wx.Frame.__init__(self, parent, title=title, size=(200,100))
   7         self.control = wx.TextCtrl(self, style=wx.TE_MULTILINE)
   8         self.Show(True)
   9 
  10 app = wx.App(False)
  11 frame = MyFrame(None, 'Small editor')
  12 app.MainLoop()

In this example, we derive from wx.Frame and overwrite its __init__ method. Here we declare a new wx.TextCtrl which is a simple text edit control. Note that since the MyFrame runs self.Show() inside its __init__ method, we no longer have to call frame.Show() explicitly.

Adding a menu bar

Every application should have a menu bar and a status bar. Let's add them to ours:

   1 import wx
   2 
   3 class MainWindow(wx.Frame):
   4     def __init__(self, parent, title):
   5         wx.Frame.__init__(self, parent, title=title, size=(200,100))
   6         self.control = wx.TextCtrl(self, style=wx.TE_MULTILINE)
   7         self.CreateStatusBar() # A Statusbar in the bottom of the window
   8 
   9         # Setting up the menu.
  10         filemenu= wx.Menu()
  11 
  12         # wx.ID_ABOUT and wx.ID_EXIT are standard IDs provided by wxWidgets.
  13         filemenu.Append(wx.ID_ABOUT, "&About"," Information about this program")
  14         filemenu.AppendSeparator()
  15         filemenu.Append(wx.ID_EXIT,"E&xit"," Terminate the program")
  16 
  17         # Creating the menubar.
  18         menuBar = wx.MenuBar()
  19         menuBar.Append(filemenu,"&File") # Adding the "filemenu" to the MenuBar
  20         self.SetMenuBar(menuBar)  # Adding the MenuBar to the Frame content.
  21         self.Show(True)
  22 
  23 app = wx.App(False)
  24 frame = MainWindow(None, "Sample editor")
  25 app.MainLoop()

TIP: Notice the wx.ID_ABOUT and wx.ID_EXIT ids. These are standard ids provided by wxWidgets (see a full list here). It is a good habit to use the standard ID if there is one available. This helps wxWidgets know how to display the widget in each platform to make it look more native.

Event handling

Reacting to events in wxPython is called event handling. An event is when "something" happens on your application (a button click, text input, mouse movement, etc). Much of GUI programming consists of responding to events. You bind an object to an event using the Bind() method:

   1 class MainWindow(wx.Frame):
   2     def __init__(self, parent, title):
   3         wx.Frame.__init__(self,parent, title=title, size=(200,100))
   4         ...
   5         menuItem = filemenu.Append(wx.ID_ABOUT, "&About"," Information about this program")
   6         self.Bind(wx.EVT_MENU, self.OnAbout, menuItem)

This means that, from now on, when the user selects the "About" menu item, the method self.OnAbout will be executed. wx.EVT_MENU is the "select menu item" event. wxWidgets understands many other events (see the full list). The self.OnAbout method has the general declaration:

   1 def OnAbout(self, event):
   2         ...

Here event is an instance of a subclass of wx.Event. For example, a button-click event - wx.EVT_BUTTON - is a subclass of wx.Event.

The method is executed when the event occurs. By default, this method will handle the event and the event will stop after the callback finishes. However, you can "skip" an event with event.Skip(). This causes the event to go through the hierarchy of event handlers. For example:

   1 def OnButtonClick(self, event):
   2     if (some_condition):
   3         do_something()
   4     else:
   5         event.Skip()
   6 
   7 def OnEvent(self, event):
   8     ...

When a button-click event occurs, the method OnButtonClick gets called. If some_condition is true, we do_something() otherwise we let the event be handled by the more general event handler. Now let's have a look at our application:

   1 import os
   2 import wx
   3 
   4 
   5 class MainWindow(wx.Frame):
   6     def __init__(self, parent, title):
   7         wx.Frame.__init__(self, parent, title=title, size=(200,100))
   8         self.control = wx.TextCtrl(self, style=wx.TE_MULTILINE)
   9         self.CreateStatusBar() # A StatusBar in the bottom of the window
  10 
  11         # Setting up the menu.
  12         filemenu= wx.Menu()
  13 
  14         # wx.ID_ABOUT and wx.ID_EXIT are standard ids provided by wxWidgets.
  15         menuAbout = filemenu.Append(wx.ID_ABOUT, "&About"," Information about this program")
  16         menuExit = filemenu.Append(wx.ID_EXIT,"E&xit"," Terminate the program")
  17 
  18         # Creating the menubar.
  19         menuBar = wx.MenuBar()
  20         menuBar.Append(filemenu,"&File") # Adding the "filemenu" to the MenuBar
  21         self.SetMenuBar(menuBar)  # Adding the MenuBar to the Frame content.
  22 
  23         # Set events.
  24         self.Bind(wx.EVT_MENU, self.OnAbout, menuAbout)
  25         self.Bind(wx.EVT_MENU, self.OnExit, menuExit)
  26 
  27         self.Show(True)
  28 
  29     def OnAbout(self,e):
  30         # A message dialog box with an OK button. wx.OK is a standard ID in wxWidgets.
  31         dlg = wx.MessageDialog( self, "A small text editor", "About Sample Editor", wx.OK)
  32         dlg.ShowModal() # Show it
  33         dlg.Destroy() # finally destroy it when finished.
  34 
  35     def OnExit(self,e):
  36         self.Close(True)  # Close the frame.
  37 
  38 app = wx.App(False)
  39 frame = MainWindow(None, "Sample editor")
  40 app.MainLoop()

Note: Instead of

   1 wx.MessageDialog( self, "A small editor in wxPython", "About Sample Editor", wx.OK)

We could have omitted the id. In that case wxWidget automatically generates an ID (just as if you specified wx.ID_ANY):

   1 wx.MessageDialog( self, "A small editor in wxPython", "About Sample Editor")

Dialogs

Of course an editor is useless if it is not able to save or open documents. That's where Common dialogs come in. Common dialogs are those offered by the underlying platform so that your application will look exactly like a native application. Here is the implementation of the OnOpen method in MainWindow:

   1     def OnOpen(self,e):
   2         """ Open a file"""
   3         self.dirname = ''
   4         dlg = wx.FileDialog(self, "Choose a file", self.dirname, "", "*.*", wx.FD_OPEN)
   5         if dlg.ShowModal() == wx.ID_OK:
   6             self.filename = dlg.GetFilename()
   7             self.dirname = dlg.GetDirectory()
   8             f = open(os.path.join(self.dirname, self.filename), 'r')
   9             self.control.SetValue(f.read())
  10             f.close()
  11         dlg.Destroy()

Explanation:

• First, we create the dialog by calling the appropriate Constructor.

• Then, we call ShowModal. That opens the dialog - "Modal" means that the user cannot do anything on the application until he clicks OK or Cancel.

• The return value of ShowModal is the Id of the button pressed. If the user pressed OK we read the file.

You should now be able to add the corresponding entry into the menu and connect it to the OnOpen method. If you have trouble, scroll down to the appendix for the full source code.

Possible extensions

Of course, this program is far from being a decent editor. But adding other features should not be any more difficult than what has already been done. You might take inspiration from the demos that are bundled with wxPython:

• Drag and Drop.
• MDI
• Tab view/multiple files
• Find/Replace dialog

• Print dialog (Printing)

• Macro-commands in python ( using the eval function)
• etc ...

Working with Windows

• Topics:

  • Frames
  • Windows
  • Controls/Widgets
  • Sizers
  • Validators

In this section, we are going to present the way wxPython deals with windows and their contents, including building input forms and using various widgets/controls. We are going to build a small application that calculates the price of a quote. If you are already an experienced GUI developer, this is going to be easy and you might want to move on to the Boa-Constructor Subsection in the Advanced topics chapter.

Overview

Laying out Visual Elements

• Within a frame, you'll use a number of wxWindow sub-classes to flesh out the frame's contents. Here are some of the more common elements you might want to put in your frame:

  • A wx.MenuBar, which puts a menu bar along the top of your frame.

  • A wx.StatusBar, which sets up an area along the bottom of your frame for displaying status messages, etc.

  • A wx.ToolBar, which puts a toolbar in your frame.

  • Sub-classes of wx.Control. These are objects which represent user interface widgets (ie, visual elements which display data and/or process user input). Common examples of wx.Control objects include wx.Button, wx.StaticText, wx.TextCtrl and wx.ComboBox.

  • A wx.Panel, which is a container to hold your various wx.Control objects. Putting your wx.Control objects inside a wx.Panel means that the user can tab from one UI widget to the next.

  All visual elements (wxWindow objects and their subclasses) can hold sub-elements. Thus, for example, a wx.Frame might hold a number of wx.Panel objects, which in turn hold a number of wx.Button, wx.StaticText and wx.TextCtrl objects, giving you an entire hierarchy of elements: Note that this merely describes the way that certain visual elements are interrelated -- not how they are visually laid out within the frame. To handle the layout of elements within a frame, you have several options:

  1. You can manually position each element by specifying it's exact pixel coordinate within the parent window. Because of differences in font sizes, etc, between platforms, this option is not generally recommended.

  2. You can use wx.LayoutConstraints, though these are fairly complex to use.

  3. You can use the Delphi-like LayoutAnchors, which make it easier to use wx.LayoutConstraints.

  4. You can use one of the wxSizer subclasses.
  This document will concentrate on the use of wxSizers, because that's the scheme I'm most familiar with.

  • TODO: Add description for other element placement schemes???. To get the first impression about other element placement schemes: http://wxpython.org/tut-part2.php

Sizers

• A sizer (that is, one of the wx.Sizer sub-classes) can be used to handle the visual arrangement of elements within a window or frame. Sizers can:

  • Calculate an appropriate size for each visual element.
  • Position the elements according to certain rules.
  • Dynamically resize and/or reposition elements when a frame is resized.
  Some of the more common types of sizers include:

  • wx.BoxSizer, which arranges visual elements in a line going either horizontally or vertically.

  • wx.GridSizer, which lays visual elements out into a grid-like structure.

  • wx.FlexGridSizer, which is similar to a wx.GridSizer except that it allow for more flexibility in laying out visual elements.

  A sizer is given a list of wx.Window objects to size, either by calling sizer.Add(window, options...), or by calling sizer.AddMany(...). A sizer will only work on those elements which it has been given. Sizers can be nested. That is, you can add one sizer to another sizer, for example to have two rows of buttons (each laid out by a horizontal wx.BoxSizer) contained within another wx.BoxSizer which places the rows of buttons one above the other, like this:

  • Note: Notice that the above example does not lay out the six buttons into two rows of three columns each -- to do that, you should use a wxGridSizer.

  In the following example we use two nested sizers, the main one with vertical layout and the embedded one with horizontal layout:

   1 import wx
   2 import os
   3 
   4 class MainWindow(wx.Frame):
   5     def __init__(self, parent, title):
   6         self.dirname=''
   7 
   8         # A "-1" in the size parameter instructs wxWidgets to use the default size.
   9         # In this case, we select 200px width and the default height.
  10         wx.Frame.__init__(self, parent, title=title, size=(200,-1))
  11         self.control = wx.TextCtrl(self, style=wx.TE_MULTILINE)
  12         self.CreateStatusBar() # A Statusbar in the bottom of the window
  13 
  14         # Setting up the menu.
  15         filemenu= wx.Menu()
  16         menuOpen = filemenu.Append(wx.ID_OPEN, "&Open"," Open a file to edit")
  17         menuAbout= filemenu.Append(wx.ID_ABOUT, "&About"," Information about this program")
  18         menuExit = filemenu.Append(wx.ID_EXIT,"E&xit"," Terminate the program")
  19 
  20         # Creating the menubar.
  21         menuBar = wx.MenuBar()
  22         menuBar.Append(filemenu,"&File") # Adding the "filemenu" to the MenuBar
  23         self.SetMenuBar(menuBar)  # Adding the MenuBar to the Frame content.
  24 
  25         # Events.
  26         self.Bind(wx.EVT_MENU, self.OnOpen, menuOpen)
  27         self.Bind(wx.EVT_MENU, self.OnExit, menuExit)
  28         self.Bind(wx.EVT_MENU, self.OnAbout, menuAbout)
  29 
  30         self.sizer2 = wx.BoxSizer(wx.HORIZONTAL)
  31         self.buttons = []
  32         for i in range(0, 6):
  33             self.buttons.append(wx.Button(self, -1, "Button &"+str(i)))
  34             self.sizer2.Add(self.buttons[i], 1, wx.EXPAND)
  35 
  36         # Use some sizers to see layout options
  37         self.sizer = wx.BoxSizer(wx.VERTICAL)
  38         self.sizer.Add(self.control, 1, wx.EXPAND)
  39         self.sizer.Add(self.sizer2, 0, wx.EXPAND)
  40 
  41         #Layout sizers
  42         self.SetSizer(self.sizer)
  43         self.SetAutoLayout(1)
  44         self.sizer.Fit(self)
  45         self.Show()
  46 
  47     def OnAbout(self,e):
  48         # Create a message dialog box
  49         dlg = wx.MessageDialog(self, " A sample editor \n in wxPython", "About Sample Editor", wx.OK)
  50         dlg.ShowModal() # Shows it
  51         dlg.Destroy() # finally destroy it when finished.
  52 
  53     def OnExit(self,e):
  54         self.Close(True)  # Close the frame.
  55 
  56     def OnOpen(self,e):
  57         """ Open a file"""
  58         dlg = wx.FileDialog(self, "Choose a file", self.dirname, "", "*.*", wx.FD_OPEN)
  59         if dlg.ShowModal() == wx.ID_OK:
  60             self.filename = dlg.GetFilename()
  61             self.dirname = dlg.GetDirectory()
  62             f = open(os.path.join(self.dirname, self.filename), 'r')
  63             self.control.SetValue(f.read())
  64             f.close()
  65         dlg.Destroy()
  66 
  67 app = wx.App(False)
  68 frame = MainWindow(None, "Sample editor")
  69 app.MainLoop()

• The sizer.Add method has three arguments. The first one specifies the control to include in the sizer. The second one is a weight factor which means that this control will be sized in proportion to other ones. For example, if you had three edit controls and you wanted them to have the proportions 3:2:1 then you would specify these factors as arguments when adding the controls. 0 means that this control or sizer will not grow. The third argument is normally wx.GROW (same as wx.EXPAND) which means the control will be resized when necessary. If you use wx.SHAPED instead, the controls aspect ratio will remain the same.

• If the second parameter is 0, i.e. the control will not be resized, the third parameter may indicate if the control should be centered horizontally and/or vertically by using wx.ALIGN_CENTER_HORIZONTAL, wx.ALIGN_CENTER_VERTICAL, or wx.ALIGN_CENTER (for both) instead of wx.GROW or wx.SHAPED as that third parameter.

• You can alternatively specify combinations of wx.ALIGN_LEFT, wx.ALIGN_TOP, wx.ALIGN_RIGHT, and wx.ALIGN_BOTTOM. The default behavior is equivalent to wx.ALIGN_LEFT | wx.ALIGN_TOP.

• One potentially confusing aspect of the wx.Sizer and its sub-classes is the distinction between a sizer and a parent window. When you create objects to go inside a sizer, you do not make the sizer the object's parent window. A sizer is a way of laying out windows, it is not a window in itself. In the above example, all six buttons would be created with the parent window being the frame or window which encloses the buttons -- not the sizer. If you try to create a visual element and pass the sizer as the parent window, your program will crash.

• Once you have set up your visual elements and added them to a sizer (or to a nested set of sizers), the next step is to tell your frame or window to use the sizer. You do this in three steps:

   1 window.SetSizer(sizer)
   2 window.SetAutoLayout(True)
   3 sizer.Fit(window)

• The SetSizer() call tells your window (or frame) which sizer to use. The call to SetAutoLayout() tells your window to use the sizer to position and size your components. And finally, the call to sizer.Fit() tells the sizer to calculate the initial size and position for all its elements. If you are using sizers, this is the normal process you would go through to set up your window or frame's contents before it is displayed for the first time.

Menus

• TODO:

Validators

• When you create a dialog box or other input form, you can use a wx.Validator to simplify the process of loading data into your form, validating the entered data, and extracting the data out of the form again. wx.Validator can also be used to intercept keystrokes and other events within an input field. To use a validator, you have to create your own sub-class of wx.Validator (neither wx.TextValidator nor wx.GenericValidator are implemented in wxPython). This sub-class is then associated with your input field by calling myInputField.SetValidator(myValidator).

  • Note: Your wx.Validator sub-class must implement the wxValidator.Clone() method.

A Working Example

Our first label within a panel

• Let's start with an example. Our program is going to have a single Frame with a panel [7] containing a label [8]:

   1 import wx
   2 class ExampleFrame(wx.Frame):
   3     def __init__(self, parent):
   4         wx.Frame.__init__(self, parent)
   5         panel = wx.Panel(self)
   6         self.quote = wx.StaticText(panel, label="Your quote: ", pos=(20, 30))
   7         self.Show()
   8 
   9 app = wx.App(False)
  10 ExampleFrame(None)
  11 app.MainLoop()

• This design should be clear and you should not have any problem with it if you read the Small Editor section of this howto. Note: a sizer should be used here instead of specifying the position of each widget. Notice in the line:

   1         self.quote = wx.StaticText(panel, label="Your quote: ", pos=(20, 30))

• the use of panel as parent parameter of our wxStaticText. Our Static text is going to be on the panel we have created just before. The wxPoint is used as positioning parameter. There is also an optional wxSize parameter but its use here is not justified.

[7] According to wxPython documentation:

• "A panel is a window on which controls are placed. It is usually placed within a frame. It contains minimal extra functionality over and above its parent class wxWindow; its main purpose is to be similar in appearance and functionality to a dialog, but with the flexibility of having any window as a parent.", in fact, it is a simple window used as a (grayed) background for other objects which are meant to deal with data entry. These are generally known as Controls or Widgets.

[8] A label is used to display text that is not supposed to interact with the user.

Adding a few more controls

• You will find a complete list of the numerous Controls that exist in wxPython in the demo and help, but here we are going to present those most frequently used:

  • wxButton The most basic Control: A button showing a text that you can click. For example, here is a "Clear" button (e.g. to clear a text):

   1 clearButton = wx.Button(self, wx.ID_CLEAR, "Clear")
   2 self.Bind(wx.EVT_BUTTON, self.OnClear, clearButton)

• wxTextCtrl This control let the user input text. It generates two main events. EVT_TEXT is called whenever the text changes. EVT_CHAR is called whenever a key has been pressed.

   1 textField = wx.TextCtrl(self)
   2 self.Bind(wx.EVT_TEXT, self.OnChange, textField)
   3 self.Bind(wx.EVT_CHAR, self.OnKeyPress, textField)

• For example: If the user presses the "Clear" button and that clears the text field, that will generate an EVT_TEXT event, but not an EVT_CHAR event.

• wxComboBox A combobox is very similar to wxTextCtrl but in addition to the events generated by wxTextCtrl, wxComboBox has the EVT_COMBOBOX event.

• wxCheckBox The checkbox is a control that gives the user true/false choice.

• wxRadioBox The radiobox lets the user choose from a list of options.

• Let's have a closer look at what Form1 looks like now:

   1 import wx
   2 class ExamplePanel(wx.Panel):
   3     def __init__(self, parent):
   4         wx.Panel.__init__(self, parent)
   5         self.quote = wx.StaticText(self, label="Your quote :", pos=(20, 30))
   6 
   7         # A multiline TextCtrl - This is here to show how the events work in this program, don't pay too much attention to it
   8         self.logger = wx.TextCtrl(self, pos=(300,20), size=(200,300), style=wx.TE_MULTILINE | wx.TE_READONLY)
   9 
  10         # A button
  11         self.button =wx.Button(self, label="Save", pos=(200, 325))
  12         self.Bind(wx.EVT_BUTTON, self.OnClick,self.button)
  13 
  14         # the edit control - one line version.
  15         self.lblname = wx.StaticText(self, label="Your name :", pos=(20,60))
  16         self.editname = wx.TextCtrl(self, value="Enter here your name", pos=(150, 60), size=(140,-1))
  17         self.Bind(wx.EVT_TEXT, self.EvtText, self.editname)
  18         self.Bind(wx.EVT_CHAR, self.EvtChar, self.editname)
  19 
  20         # the combobox Control
  21         self.sampleList = ['friends', 'advertising', 'web search', 'Yellow Pages']
  22         self.lblhear = wx.StaticText(self, label="How did you hear from us ?", pos=(20, 90))
  23         self.edithear = wx.ComboBox(self, pos=(150, 90), size=(95, -1), choices=self.sampleList, style=wx.CB_DROPDOWN)
  24         self.Bind(wx.EVT_COMBOBOX, self.EvtComboBox, self.edithear)
  25         self.Bind(wx.EVT_TEXT, self.EvtText,self.edithear)
  26 
  27         # Checkbox
  28         self.insure = wx.CheckBox(self, label="Do you want Insured Shipment ?", pos=(20,180))
  29         self.Bind(wx.EVT_CHECKBOX, self.EvtCheckBox, self.insure)
  30 
  31         # Radio Boxes
  32         radioList = ['blue', 'red', 'yellow', 'orange', 'green', 'purple', 'navy blue', 'black', 'gray']
  33         rb = wx.RadioBox(self, label="What color would you like ?", pos=(20, 210), choices=radioList,  majorDimension=3,
  34                          style=wx.RA_SPECIFY_COLS)
  35         self.Bind(wx.EVT_RADIOBOX, self.EvtRadioBox, rb)
  36 
  37     def EvtRadioBox(self, event):
  38         self.logger.AppendText('EvtRadioBox: %d\n' % event.GetInt())
  39     def EvtComboBox(self, event):
  40         self.logger.AppendText('EvtComboBox: %s\n' % event.GetString())
  41     def OnClick(self,event):
  42         self.logger.AppendText(" Click on object with Id %d\n" %event.GetId())
  43     def EvtText(self, event):
  44         self.logger.AppendText('EvtText: %s\n' % event.GetString())
  45     def EvtChar(self, event):
  46         self.logger.AppendText('EvtChar: %d\n' % event.GetKeyCode())
  47         event.Skip()
  48     def EvtCheckBox(self, event):
  49         self.logger.AppendText('EvtCheckBox: %d\n' % event.Checked())
  50 
  51 
  52 app = wx.App(False)
  53 frame = wx.Frame(None)
  54 panel = ExamplePanel(frame)
  55 frame.Show()
  56 app.MainLoop()

• Our class has grown a lot bigger; it has now a lot of controls and

  those controls react. We have added a special wxTextCtrl control to show the various events that are sent by the controls.

The notebook

• Sometimes, a form grows too big to fit on a single page. The

  wxNoteBook is used in that kind of case : It allows the user to navigate quickly between a small amount of pages by clicking on associated tabs. We implement this by putting the wxNotebook instead of our form into the main Frame and then add our Form1 into the notebook by using method AddPage.

Note how ExamplePanel's parent is the Notebook. This is important.

   1 app = wx.App(False)
   2 frame = wx.Frame(None, title="Demo with Notebook")
   3 nb = wx.Notebook(frame)
   4 
   5 
   6 nb.AddPage(ExamplePanel(nb), "Absolute Positioning")
   7 nb.AddPage(ExamplePanel(nb), "Page Two")
   8 nb.AddPage(ExamplePanel(nb), "Page Three")
   9 frame.Show()
  10 app.MainLoop()

Improving the layout - Using Sizers

• Using absolute positioning is often not very satisfying: The result is ugly if the windows are not (for one reason or another) the

  right size. WxPython has very rich vocabulary of objects to lay out controls.

  • wx.BoxSizer is the most common and simple layout object but it permits a vast range of possibilities. Its role is roughly to arrange a set of controls in a line or in a row and rearrange them when needed (i.e. when the global size is changed).

  • wx.GridSizer and wx.FlexGridSizer are two very important layout tools. They arrange the controls in a tabular layout.

Here is the sample above re-written to use sizers: