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"""
Tiny application: convert length measurements from one unit system to another
Select the input and output units using the drop down combo-boxes in the
*Input:* and *Output:* sections respectively. Type the input quantity
to convert into the left most text box. The output value corresponding to the
current input value will automatically be updated in the *Output:*
section.
Use the *Undo* and *ReDo* buttons to undo and redo changes you
have made to any of the input fields.
Note that other than the 'output_amount' property implementation, the rest
of the code is simply declarative.
"""
# FIXME: Help is broken in QT
from traits.api import HasStrictTraits, Trait, CFloat, Property
from traitsui.api import View, VGroup, HGroup, Item
# Help text:
ViewHelp = """
This program converts length measurements from one unit system to another.
Select the input and output units using the drop down combo-boxes in the
*Input:* and *Output:* sections respectively. Type the input quantity
to convert into the left most text box. The output value corresponding to the
current input value will automatically be updated in the *Output:*
section.
Use the *Undo* and *ReDo* buttons to undo and redo changes you
have made to any of the input fields.
"""
# Units trait maps all units to centimeters:
Units = Trait( 'inches', { 'inches': 2.54,
'feet': (12 * 2.54),
'yards': (36 * 2.54),
'miles': (5280 * 12 * 2.54),
'millimeters': 0.1,
'centimeters': 1.0,
'meters': 100.0,
'kilometers': 100000.0 } )
# Converter Class:
class Converter ( HasStrictTraits ):
# Trait definitions:
input_amount = CFloat( 12.0, desc = "the input quantity" )
input_units = Units( 'inches', desc = "the input quantity's units" )
output_amount = Property( depends_on = [ 'input_amount', 'input_units',
'output_units' ],
desc = "the output quantity" )
output_units = Units( 'feet', desc = "the output quantity's units" )
# User interface views:
traits_view = View(
VGroup(
HGroup(
Item( 'input_amount', springy = True ),
Item( 'input_units', show_label = False ),
label = 'Input',
show_border = True
),
HGroup(
Item( 'output_amount', style = 'readonly', springy = True ),
Item( 'output_units', show_label = False ),
label = 'Output',
show_border = True
),
help = ViewHelp
),
title = 'Units Converter',
buttons = [ 'Undo', 'OK', 'Help' ]
)
# Property implementations
def _get_output_amount ( self ):
return ((self.input_amount * self.input_units_) / self.output_units_)
# Create the demo:
popup = Converter()
# Run the demo (if invoked from the command line):
if __name__ == '__main__':
popup.configure_traits()
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