Creating Thick Client Apps Quickly with PythonCard

by Ralph Heimburger

September 17, 2009

Introduction

PythonCard is a GUI construction toolkit written entirely in Python that offers a cross-platform rapid GUI development with an intuitive interface. Inspired by Apple's Hypercard, PythonCard separates the GUI components from the event driven code.

When I first found PythonCard I was looking for a rapid application GUI toolkit that followed some of the design promises of Python, one being "it gets out of your way and allows you to code". I quickly found that this GUI toolkit offered a very intuitive interface and I was able to quickly write functional applications for a variety of purposes. PythonCard comes with very good code samples that allow developers to quickly get up and running.

Getting Started

To install PythonCard, there are some requirements. First, you will need Python itself, version 2.5 or higher, then wxPython, which is the underlying library which PythonCard runs on. And lastly, of course is PythonCard.

Note: If you are developing on a Windows platform you will find installers for each of these.

Creating your first PythonCard application

The first step in creating any application is to determine it's basic functionality. Although PythonCard offers a lot of basic components, it may not fit your applications' design goals, so consider the audience of your application before deciding which toolkit to use.

Using the Resource Editor

The GUI construction component of PythonCard is called the Resource Editor. When you open it you will see a basic empty template where you can begin entering components, e.g. TextFields, Buttons, Lists, etc. The Resource Editor has 2 screens, the Resource Editor and the Property Editor. The Property Editor allows you to modify the properties (size, color, font, command, etc) of the components you add via the Resource Editor. The components PythonCard exposes are a subset of the wxPython library. PythonCard does not restrict you from going beyond these basic controls, but it gives you a rich set of the basic library. Again, PythonCard is a Rapid GUI construction toolkit and intended to be so.

If this is a new application, the Resource Editor will save 2 files for your application, one being the application main python file and a resource file. Assume that your application is named myapp, you will see myapp.py and myapp.rsrc.py. This is by design and allows you to focus your development and testing through myapp.py and changing GUI components via myapp.rsrc.py.

Resource Editor:

Property Editor (ClickMe button)

First look at the Resource Editor generated code.

      #!/usr/bin/python
      
      """
      __version__ = "$Revision: 1.5 $"
      __date__ = "$Date: 2004/04/30 16:26:12 $"
      """
      
      from PythonCard import model
      
      class MyBackground(model.Background):
      
          def on_initialize(self, event):
              # if you have any initialization
              # including sizer setup, do it here
              pass
      
      
      if __name__ == '__main__':
          app = model.Application(MyBackground)
          app.MainLoop()

PythonCard creates the "shell" for the GUI application that when invoked from the command prompt by typing 'myapp.py', will essentially do nothing because there are no event handlers coded yet.

Adding the event code for the ClickMe button

I decided that when the ClickMe button is clicked, I want to respond with a dialog box. Again, this is an introductory example to demonstrate and introduce PythonCard. I bolded the code sample below where I added the additional code.

      #!/usr/bin/python
      
      """
      __version__ = "$Revision: 1.5 $"
      __date__ = "$Date: 2004/04/30 16:26:12 $"
      """
      
      from PythonCard import model, dialog 
      
      class MyBackground(model.Background):
      
          def on_initialize(self, event):
              # if you have any initialization
              # including sizer setup, do it here
              pass
      
        def on_ClickMe_command(self, event):
              about="This application now works.\nyou clicked Me!"
              dlg = dialog.scrolledMessageDialog(self, about, 'ClickMe')
              return 
      
      
      if __name__ == '__main__':
          app = model.Application(MyBackground)
          app.MainLoop()

How it looks

Summary

The completed myapp.py contains 25 lines of highly readable and maintainable code. The resource or 'rsrc' file is 44 lines. PythonCard apps can also be compiled to executables using either Py2exe or cx_freeze so they can be distributed as standalone GUI applications.