parserutils.py 文件源码

def value(ctx, val, variables=False, errors=False):

    """
    utility function for evaluating something...

    Variables will be looked up in the context
    Normally, non-bound vars is an error,
    set variables=True to return unbound vars

    Normally, an error raises the error,
    set errors=True to return error

    """

    if isinstance(val, Expr):
        return val.eval(ctx)  # recurse?
    elif isinstance(val, CompValue):
        raise Exception("What do I do with this CompValue? %s" % val)

    elif isinstance(val, list):
        return [value(ctx, x, variables, errors) for x in val]

    elif isinstance(val, (BNode, Variable)):
        r = ctx.get(val)
        if isinstance(r, SPARQLError) and not errors:
            raise r
        if r is not None:
            return r

        # not bound
        if variables:
            return val
        else:
            raise NotBoundError

    elif isinstance(val, ParseResults) and len(val) == 1:
        return value(ctx, val[0], variables, errors)
    else:
        return val