root/trunk/zoo.py

import datetime
try:
    import fixedpoint
except ImportError:
    fixedpoint = None

try:
    import decimal
except ImportError:
    decimal = None

import dejavu
from dejavu import Unit, UnitProperty, associate


class Zoo(Unit):
    Name = UnitProperty()
    Founded = UnitProperty(datetime.date)
    Opens = UnitProperty(datetime.time)
    LastEscape = UnitProperty(datetime.datetime)
    
    if fixedpoint:
        Admission = UnitProperty(fixedpoint.FixedPoint)
    else:
        Admission = UnitProperty(float)


class EscapeProperty(UnitProperty):
    def __set__(self, unit, value):
        UnitProperty.__set__(self, unit, value)
        z = unit.first(Zoo)
        if z:
            z.LastEscape = unit.LastEscape

class Animal(Unit):
    Name = UnitProperty()
    ZooID = UnitProperty(int, index=True)
    Legs = UnitProperty(int)
    PreviousZoos = UnitProperty(list)
    LastEscape = EscapeProperty(datetime.datetime)
    Lifespan = UnitProperty(float, hints={'bytes': 4})
    
    def in_first_zoo(self):
        return (self.PreviousZoo and self.PreviousZoo[0] == self.ZooID)

associate(Zoo, 'ID', Animal, 'ZooID')


class Exhibit(Unit):
    # Make this a string to help test vs unicode.
    Name = UnitProperty(str)
    ZooID = UnitProperty(int)
    Animals = UnitProperty(list)
    PettingAllowed = UnitProperty(bool)
    if decimal:
        Acreage = UnitProperty(decimal.Decimal)
    else:
        Acreage = UnitProperty(float)

associate(Zoo, 'ID', Exhibit, 'ZooID')

arena = dejavu.Arena()
arena.register_all(globals())