[http://code.enthought.com/traits/ TraitsUI] is a module that allows automatic generation of [http://www.wxpython.org WxPython] dialogs to edit the properties of objects.

It makes building interactive graphical user interfaces much easier than working directly with the widgets.

This page is nothing but a short introduction. A step-by-step tutorial on building an interactive scientific application with TraitsUI is available at: http://gael-varoquaux.info/computers/traits_tutorial/index.html .

= The configure_traits dialog =
A "traited" object is an object whose attributes have been specified beforehand.

{{{
#!python numbers=disable
from enthought.traits.api import Str, Int, HasTraits
class Person(HasTraits):
    age = Int
    name = Str
}}}
The "!HasTraits" metaclass will check that the values the attributes are set to correspond to the object's definition.

{{{
#!python numbers=disable
>>> joe = Person()
>>> joe.name = "joe"
>>> joe.age = "1"
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python2.4/site-packages/enthought/traits/trait_handlers.py", line 171, in error
    raise TraitError, ( object, name, self.info(), value )
enthought.traits.trait_errors.TraitError: The 'age' trait of a Person instance must be a value of type 'int', but a value of 1 was specified.
}}}
A traited object has a method that can display a dialog to edit its attributes:

{{{
#!python numbers=disable
>>> joe.configure_traits()
}}}
attachment:configure_traits.png

= Interactive dialogs =
The "configure_traits" method does not fit in a larger UI, it creates a UI, with its event-loop, and closes it once the dialog is closed. It fits in purely sequential batch programming.

Using a few simple modification notifications makes the application interactive:

{{{
#!python numbers=disable
from enthought.traits.api import Str, Float, HasTraits
class UnitConverter(HasTraits):
    pounds = Float(0, desc="Weight in pounds")
    kilogrammes  = Float(0, desc="Weight in kilogrammes")
    def _pounds_changed(self, value):
        self.kilogrammes = value/2.2
    def _kilogrammes_changed(self, value):
        self.pounds = value*2.2
UnitConverter().configure_traits()
}}}
attachment:unit_converter.png

An "edit_traits" method is available to create a dialog that will be part of the !WxPython event-loop. You can use it in "ipython -wthread", that has the !WxPython loop running, or in a larger !WxPython  application. The tutorial shows how to integrate traits and matplotlib plots. [:EmbeddingInTraitsGUI:Here's] another recipe for embedding a matplotlib figure in a TraitsUI app.

The examples shown here are very basic, but the traits module provides many more tools and features that help building a fully-fledged application for scientific purposes.