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from datetime import datetime
from sqlalchemy import Column, Integer, Float, DateTime, String, ForeignKey
from sqlalchemy.orm import relationship, backref
from sqlalchemy.ext.declarative import declarative_base
ModelBase = declarative_base()
class Sensor(ModelBase):
__tablename__ = 'sensor'
id = Column(Integer, primary_key=True)
name = Column(String)
description = Column(String, default="")
def __init__(self, name, description=""):
self.name = name
self.description = description
def __repr__(self):
return "<Sensor('%s','%s','%s')>" % (self.id, self.name, self.description)
# http://www.sqlalchemy.org/docs/05/reference/ext/declarative.html#inheritance-configuration
class Value(ModelBase):
__tablename__ = 'value'
id = Column(Integer, primary_key=True)
timestamp = Column(DateTime)
sensor_id = Column(Integer, ForeignKey("sensor.id"))
sensor = relationship(Sensor, backref=backref('values', order_by=timestamp))
discriminator = Column('type', String(50))
__mapper_args__ = {'polymorphic_on': discriminator}
def __init__(self, sensor, timestamp=datetime.now()):
self.timestamp = timestamp
self.sensor = sensor
def __repr__(self):
return "<Value('%s','%s','%s','%s'>" % (self.id, self.sensor, self.value, self.timestamp)
def value(self):
raise NotImplementedException()
class ValueFloat(Value):
__mapper_args__ = {'polymorphic_identity': 'float'}
value_float = Column(Float(precision=4))
def __init__(self, sensor, value, timestamp=datetime.now()):
Value.__init__(self, sensor, timestamp)
self.value_float = value
def value(self):
return self.value_float
class ValueInt(Value):
__mapper_args__ = {'polymorphic_identity': 'int'}
value_int = Column(Integer)
def __init__(self, sensor, value, timestamp=datetime.now()):
Value.__init__(self, sensor, timestamp)
self.value_int = value
def value(self):
return self.value_int
class ValueString(Value):
__mapper_args__ = {'polymorphic_identity': 'string'}
value_string = Column(String)
def __init__(self, sensor, value, timestamp=datetime.now()):
Value.__init__(self, sensor, timestamp)
self.value_string = value
def value(self):
return self.value_string
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