SQLAlchemy: Problems Migrating to PostgreSQL from SQLite (e.g. sqlalchemy.exc.ProgrammingError:) - postgresql

Question

I am having difficulties migrating a working a working script to PGSQL from SQLite. I am using SQLalchemy. When I run the script, it raises the following errors:
raise exc.DBAPIError.instance(statement, parameters, e, connection_invalidated=is_disconnect)
sqlalchemy.exc.ProgrammingError: (ProgrammingError) can't adapt 'INSERT INTO cnn_hot_stocks (datetime, list, ticker, price, change, "pctChange") VALUES (%(datetime)s, %(list)s, %(ticker)s, %(price)s, %(change)s, %(pctChange)s)' {'price': Decimal('7.94'), 'list': 'active', 'datetime': datetime.datetime(2012, 6, 23, 11, 45, 1, 544361), 'pctChange': u'+1.53%', 'ticker': u'BAC', 'change': Decimal('0.12')}
The insert call works well when using sqlite engine, but I want to use pgsql to utilize the native Decimal type for keeping financial data correct. I copied the script and just changed the db engine to my postgresql server. Any advice on how to troubleshoot this error would be greatly appreciated for this SQLalchemy newbie... I think I am up a creek on this one! Thanks in advance!
Here are my relevant code segments and table descriptions:
dbstring = "postgresql://postgres:postgres#localhost:5432/algo"
db = create_engine(dbstring)
db.echo = True # Try changing this to True and see what happens
metadata = MetaData(db)
cnn_hot_stocks = Table('cnn_hot_stocks', metadata, autoload=True)
i = cnn_hot_stocks.insert() # running log from cnn hot stocks web-site
def scrape_data():
try:
html = urllib2.urlopen('http://money.cnn.com/data/hotstocks/').read()
markup, errors = tidy_document(html)
soup = BeautifulSoup(markup,)
except Exception as e:
pass
list_map = { 2 : 'active',
3 : 'gainer',
4 : 'loser'
}
# Iterate over 3 tables on CNN hot stock web-site
for x in range(2, 5):
table = soup('table')[x]
for row in table.findAll('tr')[1:]:
timestamp = datetime.now()
col = row.findAll('td')
ticker = col[0].a.string
price = Decimal(col[1].span.string)
change = Decimal(col[2].span.span.string)
pctChange = col[3].span.span.string
log_data = {'datetime' : timestamp,
'list' : list_map[x],
'ticker' : ticker,
'price' : price,
'change' : change,
'pctChange' : pctChange
}
print log_data
# Commit to DB
i.execute(log_data)
TABLE:
cnn_hot_stocks = Table('cnn_hot_stocks', metadata, # log of stocks data on cnn hot stocks lists
Column('datetime', DateTime, primary_key=True),
Column('list', String), # loser/gainer/active
Column('ticker', String),
Column('price', Numeric),
Column('change', Numeric),
Column('pctChange', String),
)

Answer 1

My reading of the documentation is that you have to use numeric instead of decimal.
PostgreSQL has no type named decimal (it's an alias for numeric but not a very full-featured one), and SQL Alchemy seems to expect numeric as the type it can use for abstraction purposes.