/usr/share/doc/python-traits/examples/tutorials/traits_4.0/extended_trait_change/properties.py is in python-traits 4.1.0-1.
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# License: BSD Style.
#--(Extended Property depends_on References)------------------------------------
"""
Extended Property *depends_on* References
=========================================
In Traits 3.0, the **Property** *depends_on* metadata has been extended to
take advantage of the new extended trait name support offered by the
*on_trait_change* method.
Previously, the *depends_on* metadata for a *Property* was restricted to
referencing traits defined either on the same object as the **Property**, or
on an object immediately reachable from the object. For example::
class Wheel ( Part ):
axel = Instance( Axel )
position = Property( depends_on = 'axel.position' )
...
Starting with Traits 3.0, the *depends_on* metadata may now include any
extended trait reference that is allowed by the enhanced *on_trait_change*
method. So, for example it is now legal to write things like::
class Wheel ( Part ):
axel = Instance( Axel )
position = Property( depends_on = 'axel.chassis.position' )
or::
class Child ( Person ):
mother = Instance( Person )
father = Instance( Person )
mood = Property( depends_on = [ 'mother.+mood_affecting',
'father.+mood_affecting' ] )
In particular, in the last example we are declaring that the **Child** class's
*mood* property depends upon the values of any of either its mother or
father object's traits that have *mood_affecting* metadata defined.
Thus, a **Child** object's *mood* property will fire a trait change notification
whenever any of the its mother's or father's mood affecting traits change.
Refer also to the code tabs for this lesson for a complete example using a
**Property** definition using *depends_on* metadata containing an extended trait
reference. In particular, take a look at the **LeagueModelView Class** tab's
*total_hits* trait definition.
"""
# FIXME redo example without traitsui
#--<Imports>--------------------------------------------------------------------
from traits.api \
import *
from traitsui.api \
import *
from traitsui.table_column \
import *
#--[Player Class]---------------------------------------------------------------
# Define a baseball player:
class Player ( HasTraits ):
# The name of the player:
name = Str( '<new player>' )
# The number of hits the player made this season:
hits = Int
#--[Team Class]-----------------------------------------------------------------
# Define a baseball team:
class Team ( HasTraits ):
# The name of the team:
name = Str( '<new team>' )
# The players on the team:
players = List( Player )
# The number of players on the team:
num_players = Property( depends_on = 'players' )
def _get_num_players ( self ):
""" Implementation of the 'num_players' property.
"""
return len( self.players )
#--[League Class]---------------------------------------------------------------
# Define a baseball league model:
class League ( HasTraits ):
# The name of the league:
name = Str( '<new league>' )
# The teams in the league:
teams = List( Team )
#--[LeagueModelView Class]-----------------------------------------------------
# Define a ModelView for a League model:
class LeagueModelView ( ModelView ):
# The currently selected team:
team = Instance( Team )
# The currently selected player:
player = Instance( Player )
# Button to add a hit to the current player:
got_hit = Button( 'Got a Hit' )
# The total number of hits (note the 'depends_on' extended trait reference):
total_hits = Property( depends_on = 'model.teams.players.hits' )
@cached_property
def _get_total_hits ( self ):
""" Returns the total number of hits across all teams and players.
"""
return reduce( add, [ reduce( add, [ p.hits for p in t.players ], 0 )
for t in self.model.teams ], 0 )
view = View(
VGroup(
HGroup(
Item( 'total_hits', style = 'readonly' ),
label = 'League Statistics',
show_border = True
),
VGroup(
Item( 'model.teams',
show_label = False,
editor = TableEditor(
columns = [ ObjectColumn( name = 'name',
width = 0.70 ),
ObjectColumn( name = 'num_players',
label = '# Players',
editable = False,
width = 0.29 ) ],
selected = 'object.team',
auto_add = True,
row_factory = Team,
configurable = False,
sortable = False )
),
label = 'League Teams',
show_border = True
),
VGroup(
Item( 'object.team.players',
show_label = False,
editor = TableEditor(
columns = [ ObjectColumn( name = 'name',
width = 0.70 ),
ObjectColumn( name = 'hits',
editable = False,
width = 0.29 ) ],
selected = 'object.player',
auto_add = True,
row_factory = Player,
configurable = False,
sortable = False )
),
'_',
HGroup(
Item( 'got_hit',
show_label = False,
enabled_when = 'player is not None'
)
),
label = 'Team Players',
show_labels = False,
show_border = True
)
),
resizable = True
)
def _model_changed ( self, model ):
""" Handles the 'league' model being initialized.
"""
if len( model.teams ) > 0:
self.team = model.teams[0]
def _got_hit_changed ( self ):
""" Handles the currently selected player making a hit.
"""
self.player.hits += 1
def _team_changed ( self, team ):
""" Handles a new team being selected.
"""
if len( team.players ) > 0:
self.player = team.players[0]
else:
self.player = None
# Function to add two numbers (used with 'reduce'):
add = lambda a, b: a + b
#--[Example*]-------------------------------------------------------------------
# Define some sample teams and players:
blue_birds = Team( name = 'Blue Birds', players = [
Player( name = 'Mike Scott', hits = 25 ),
Player( name = 'Willy Shofield', hits = 37 ),
Player( name = 'Tony Barucci', hits = 19 ) ] )
chicken_hawks = Team( name = 'Chicken Hawks', players = [
Player( name = 'Jimmy Domore', hits = 34 ),
Player( name = 'Bill Janks', hits = 16 ),
Player( name = 'Tim Saunders', hits = 27 ) ] )
eagles = Team( name = 'Eagles', players = [
Player( name = 'Joe Peppers', hits = 33 ),
Player( name = 'Sam Alone', hits = 12 ),
Player( name = 'Roger Clemson', hits = 23 ) ] )
# Create a league and its corresponding model view:
demo = LeagueModelView(
League( name = 'National Baseball Conference',
teams = [ blue_birds, chicken_hawks, eagles ] )
)
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