sqlalchemy Evalulate Criteria based on list of tuple, searching?

I want to apply some access rule type of mechanism, for that I'm planning to use list of tuple for specifying rules for restrictions like below

['|',('name','=','root'), ('role','=','admin')] using postfix notations...

is there any e开发者_开发百科xisting mechanism in python that may help me to convert such domain into sqlalchemy query lang like

or_(User.name='root', User.role='admin')

Here's a start of one:

I'm going to rewrite your expression in terms of prefix notation; the operator is first and the other values follow, so:

test_expression = ['|',('=','name','root'), ('=','role','admin')]

but, you could probably add some more operator specific checks to handle operators in other locations.

def buildquery(context, expression):
    OPERATORS[expression[0]](context, expression[1:])

def build_or(context, args):
    return sqlalchemy.or_(*(buildquery(context, arg) for arg in args))

def build_eq(context, args):
    colname, value = args
    return getattr(context, colname) == value

OPERATORS = {
    '|': build_or,
    '=': build_eq}

And to use it, pass the mapped class you want to use the query with:

session.query(User).filter(build_query(User, test_expression))