correction, you'd also name the relationship "_readings", eg.
self.sensor._readings
On Thu, Jul 27, 2017 at 4:50 PM, Mike Bayer <mike...@zzzcomputing.com> wrote:
> On Thu, Jul 27, 2017 at 4:43 PM, Mike Bayer <mike...@zzzcomputing.com> wrote:
>> On Thu, Jul 27, 2017 at 10:50 AM, Ruben Di Battista
>> <rubendibatti...@gmail.com> wrote:
>>> Hello, I'm trying to figure out a streamlined way to store some children
>>> values that are stored in numpy arrays in Python. As example let's assume I
>>> have a parent object that is a sensor that has some readings associated to
>>> it:
>>>
>>> class Sensor(object):
>>> __tablename__ = 'sensor'
>>> id = Column(Integer, primary_key=True),
>>> name = Column(String)
>>> readings = relationship("Reading", backref="sensor")
>>>
>>>
>>> class Reading(object):
>>> __tablename__ = 'reading'
>>> id = Column(Integer, primary_key=True),
>>> date = Column(DateTime),
>>> voltage = Column(Float),
>>> value = Column(Float),
>>>
>>> sensor_id = Column(Integer, ForeignKey('sensor.id'))
>>>
>>>
>>> What I would like to achieve is something like:
>>> sensor = Sensor(name='Bedroom Sensor')
>>> dates, voltages, values = get_sensor_data_from_somewhere() #<-- This
>>> returns three numpy arrays respectively of datetime, float, float types,
>>> same len!
>>>
>>> sensor.readings['date'] = dates
>>> sensor.readings['voltage'] = voltages
>>> sensor.values['value'] = values
>
> oh, .readings. Unfortunately you'd need to develop a custom
> collection class which achieves this and make it available by a
> @property on Sensor:
>
> class Sensor(...):
> @property
> def readings(self):
> return MagicReadingCollection(self)
>
> then you do the __getitem__ / __setitem__ thing on MagicReadingCollection:
>
> class MagicReadingCollection(object):
> def __init__(self, sensor):
> self.sensor = sensor
>
> def __setitem__(self, field, values):
> start_appending_at = len(self.sensor.readings)
> for index, value in enumerate(values):
> if index > start_appending_at:
> reading = Reading()
> self.sensor.readings.append(reading)
> else:
> reading = self.sensor.readings[index]
> setattr(reading, field, value)
>
>
>
>
>
>
>>>
>>> session.add(sensor)
>>>
>>> Is this possible somehow? It's similar to the attribute_mapped_collection,
>>> but I need to map three different keys to the three attributes of the
>>> Reading object.
>>
>> Application of appropriate __getitem__() and __setitem__() methods on
>> your Sensor class would achieve this.
>>
>>
>>>
>>> --
>>> SQLAlchemy -
>>> The Python SQL Toolkit and Object Relational Mapper
>>>
>>> http://www.sqlalchemy.org/
>>>
>>> To post example code, please provide an MCVE: Minimal, Complete, and
>>> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
>>> description.
>>> ---
>>> You received this message because you are subscribed to the Google Groups
>>> "sqlalchemy" group.
>>> To unsubscribe from this group and stop receiving emails from it, send an
>>> email to sqlalchemy+unsubscr...@googlegroups.com.
>>> To post to this group, send email to sqlalchemy@googlegroups.com.
>>> Visit this group at https://groups.google.com/group/sqlalchemy.
>>> For more options, visit https://groups.google.com/d/optout.
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
---
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sqlalchemy+unsubscr...@googlegroups.com.
To post to this group, send email to sqlalchemy@googlegroups.com.
Visit this group at https://groups.google.com/group/sqlalchemy.
For more options, visit https://groups.google.com/d/optout.
