While it is possible to use strings in order to apply conditions to a query, it can be unsafe, because of the risk of SQL injection. The better way for applying conditions to a query is using the filter()
method. You can take the latest version of Pony ORM from https://github.com/ponyorm/pony repository and try a couple of examples provided below.
First we define entities and create a couple of objects:
from decimal import Decimal
from pony.orm import *
db = Database('sqlite', ':memory:')
class Product(db.Entity):
name = Required(unicode)
description = Required(unicode)
price = Required(Decimal)
quantity = Required(int, default=0)
db.generate_mapping(create_tables=True)
with db_session:
Product(name='iPad', description='Air, 16GB', price=Decimal('478.99'), quantity=10)
Product(name='iPad', description='Mini, 16GB', price=Decimal('284.95'), quantity=15)
Product(name='iPad', description='16GB', price=Decimal('299.00'), quantity=10)
Now we'll apply filters passing them as keyword arguments:
def find_by_kwargs(**kwargs):
q = select(p for p in Product)
q = q.filter(**kwargs)
return list(q)
with db_session:
products = find_by_kwargs(name='iPad', quantity=10)
for p in products:
print p.name, p.description, p.price, p.quantity
Another option is to use lambdas in order to specify the conditions:
def find_by_params(name=None, min_price=None, max_price=None):
q = select(p for p in Product)
if name is not None:
q = q.filter(lambda p: p.name.startswith(name))
if min_price is not None:
q = q.filter(lambda p: p.price >= min_price)
if max_price is not None:
q = q.filter(lambda p: p.price <= max_price)
return list(q)
with db_session:
products = find_by_params(name='iPad', max_price=400)
for p in products:
print p.name, p.description, p.price, p.quantity
As you can see filters can be applied dynamically. You can find more information about using filters following by this link: http://doc.ponyorm.com/queries.html#Query.filter