python - ponyORM:查询有问题

Question

我有动态条件查询，即

select (lambda obj:obj.A = 'a' and obj.B = 'b' and ...)  

所以我为此编写代码:

def search(self,**kwargs):
        q = unicode('lambda obj:', 'utf-8')
    for field,value in kwargs.iteritems():
            value = unicode(value, 'utf-8')
            field = unicode(field, 'utf-8')
            q+=u" obj.%s == '%s' and" % (field,value

    q = q[0:q.rfind('and')] 
    res = select(q.encode('utf-8'))[:]

但是我在执行函数的过程中出现了这个错误:

 tasks.search(title='Задача 1',url='test.com')
 res = select(q.encode('utf-8'))[:]
 File "<string>", line 2, in select
 File ".../local/lib/python2.7/site-packages/pony/utils.py", line 96, in      cut_traceback
return func(*args, **kwargs)
  File ".../local/lib/python2.7/site-packages/pony/orm/core.py", line 3844, in select
if not isinstance(tree, ast.GenExpr): throw(TypeError)
  File "...local/lib/python2.7/site-packages/pony/utils.py", line 123, in throw
  raise exc
  TypeError

Answer 1

虽然可以使用字符串来将条件应用于查询，但它可能不安全，因为存在 SQL 注入(inject)的风险。将条件应用于查询的更好方法是使用 filter() 方法。您可以从 https://github.com/ponyorm/pony 获取最新版本的 Pony ORM存储库并尝试下面提供的几个示例。

首先我们定义实体并创建几个对象:

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)

现在我们将应用过滤器将它们作为关键字参数传递:

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

另一种选择是使用 lambda 来指定条件:

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

如您所见，可以动态应用过滤器。您可以通过以下链接找到有关使用过滤器的更多信息:http://doc.ponyorm.com/queries.html#Query.filter