def _evaluate(self, context, query):
"""
DON'T USE THIS EXTERNALLY UNLESS YOU KNOW WHAT YOU'RE DOING. It's for
JPath internal use. I'll get a tutorial up soon on how to properly run a
query.
"""
# Figure out the method to dispatch to based on the type of AST node that
# this is
function = self.get_evaluator(type(query))
try:
if function is None:
raise Exception("Evaluate not implemented for AST component type " +
str(type(query)) + " containing " + trimTo(200, repr(query)) + ". "
+ JPATH_INTERNAL_ERROR_MESSAGE)
result = function(context, query)
if not isinstance(result, list):
raise Exception("Result was not a list (representing a collection) "
"for AST component type " + str(type(query)) + " containing " +
trimTo(200, repr(query)) + ". " + JPATH_INTERNAL_ERROR_MESSAGE)
return result
except errors.EvaluationError as e:
# TODO: in the future, add additional information to this as we travel
# up the stack
raise
except Exception as e:
if context.get_option("jpath.python_traceback", False):
print_exc()
raise errors.EvaluationError(query.parse_location, type(e).__name__ + ": " + str(e), sys.exc_info())
def get_evaluator(self, production_class):
try:
return self.evaluators[production_class]
except KeyError:
raise Exception("No evaluator could be found for production class "
+ str(type(production_class)) + ", and specifically the instance "
+ trimTo(200, repr(production_class)) + ". This means that an "
"evaluator for this production class wasn't installed "
"using set_evaluator ")