Re: [sqlalchemy] Creating one-to-many relationship: child class returns empty list after trying to enter data
On 10 Aug 2013, at 03:42, csdr...@gmail.com wrote:
This is driving me a little crazy so hopefully someone here can help. This is
my first time working with sqlalchemy (v0.8). Python is v2.7.2 and MySQL is
v14.14.
The (heavily) summarized code is as follows:
class Price(Base):
__tablename__ = prices
id = Column(Integer, primary_key = True)
company_id = Column(Integer, ForeignKey('companies.id'))
date = Column(DateTime)
close = Column(Float)
volume = Column(Integer)
def __init__(self, date, close, volume):
self.date = date
self.close = close
self.volume = volume
class Company(Base):
__tablename__ = companies
id = Column(Integer, primary_key = True)
ticker = Column(String(10))
company = Column(String(100))
prices = relationship(Price)
def __init__(self, ticker, company):
self.ticker = ticker
self.company = company
def get_prices(self):
csv_data = get_csv()
for row in csv_data:
date = row[0].strip()
date = datetime.datetime.strptime(date, '%Y-%m-%d')
close = float(row[4])
volume = int(row[5])
prices = Price(date = date, close = close, volume = volume)
session.add(prices)
So, what the code should do is have a table of companies and a table of daily
pricing data on all companies. I want to be able to access the prices via
company.prices. Instead, when I try to do this, Python returns an empty list
[]. I know that the data is getting picked up somewhere because I see the SQL
activity when I do session.commit(). I've also tried modifying the
get_prices() function by changing the prices variable to a list + append()
and then at the end of the for loop doing a session.add_all(prices), but that
didn't work either. What am I doing incorrectly?
Thanks,
Chris
You haven't associated your Price instances with the Company instance. If you
looked at the database, all the company_id values would be NULL.
If you put self.prices.append(prices) as the last line of your loop, it
should all work. In fact, if you do that, the session.add will be unnecessary
because the prices will be automatically added to the session (assuming that
the company is already in the session).
Hope that helps,
Simon
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Re: [sqlalchemy] Creating one-to-many relationship: child class returns empty list after trying to enter data
Thank you! That worked.
On Saturday, August 10, 2013 5:39:31 AM UTC-4, Simon King wrote:
On 10 Aug 2013, at 03:42, csd...@gmail.com javascript: wrote:
This is driving me a little crazy so hopefully someone here can help.
This is my first time working with sqlalchemy (v0.8). Python is v2.7.2 and
MySQL is v14.14.
The (heavily) summarized code is as follows:
class Price(Base):
__tablename__ = prices
id = Column(Integer, primary_key = True)
company_id = Column(Integer, ForeignKey('companies.id'))
date = Column(DateTime)
close = Column(Float)
volume = Column(Integer)
def __init__(self, date, close, volume):
self.date = date
self.close = close
self.volume = volume
class Company(Base):
__tablename__ = companies
id = Column(Integer, primary_key = True)
ticker = Column(String(10))
company = Column(String(100))
prices = relationship(Price)
def __init__(self, ticker, company):
self.ticker = ticker
self.company = company
def get_prices(self):
csv_data = get_csv()
for row in csv_data:
date = row[0].strip()
date = datetime.datetime.strptime(date, '%Y-%m-%d')
close = float(row[4])
volume = int(row[5])
prices = Price(date = date, close = close, volume = volume)
session.add(prices)
So, what the code should do is have a table of companies and a table of
daily pricing data on all companies. I want to be able to access the prices
via company.prices. Instead, when I try to do this, Python returns an empty
list []. I know that the data is getting picked up somewhere because I see
the SQL activity when I do session.commit(). I've also tried modifying the
get_prices() function by changing the prices variable to a list + append()
and then at the end of the for loop doing a session.add_all(prices), but
that didn't work either. What am I doing incorrectly?
Thanks,
Chris
You haven't associated your Price instances with the Company instance. If
you looked at the database, all the company_id values would be NULL.
If you put self.prices.append(prices) as the last line of your loop, it
should all work. In fact, if you do that, the session.add will be
unnecessary because the prices will be automatically added to the session
(assuming that the company is already in the session).
Hope that helps,
Simon
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[sqlalchemy] Creating one-to-many relationship: child class returns empty list after trying to enter data
This is driving me a little crazy so hopefully someone here can help. This
is my first time working with sqlalchemy (v0.8). Python is v2.7.2 and MySQL
is v14.14.
The (heavily) summarized code is as follows:
class Price(Base):
__tablename__ = prices
id = Column(Integer, primary_key = True)
company_id = Column(Integer, ForeignKey('companies.id'))
date = Column(DateTime)
close = Column(Float)
volume = Column(Integer)
def __init__(self, date, close, volume):
self.date = date
self.close = close
self.volume = volume
class Company(Base):
__tablename__ = companies
id = Column(Integer, primary_key = True)
ticker = Column(String(10))
company = Column(String(100))
prices = relationship(Price)
def __init__(self, ticker, company):
self.ticker = ticker
self.company = company
def get_prices(self):
csv_data = get_csv()
for row in csv_data:
date = row[0].strip()
date = datetime.datetime.strptime(date, '%Y-%m-%d')
close = float(row[4])
volume = int(row[5])
prices = Price(date = date, close = close, volume = volume)
session.add(prices)
So, what the code* *should do is have a table of companies and a table of
daily pricing data on all companies. I want to be able to access the prices
via company.prices. Instead, when I try to do this, Python returns an empty
list []. I know that the data is getting picked up somewhere because I see
the SQL activity when I do session.commit(). I've also tried modifying the
get_prices() function by changing the prices variable to a list + append() and
then at the end of the for loop doing a session.add_all(prices), but that
didn't work either. What am I doing incorrectly?
Thanks,
Chris
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