dianfu commented on a change in pull request #9766: [FLINK-14018][python] Add Python building blocks to make sure the basic functionality of Python ScalarFunction could work URL: https://github.com/apache/flink/pull/9766#discussion_r329335830
########## File path: flink-python/pyflink/table/udf.py ########## @@ -0,0 +1,217 @@ +################################################################################ +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you under the Apache License, Version 2.0 (the +# "License"); you may not use this file except in compliance +# with the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. +################################################################################ +import collections +import functools +import inspect +from abc import ABCMeta, abstractmethod + +from pyflink.java_gateway import get_gateway +from pyflink.table.types import DataType, _to_java_type +from pyflink.util import utils + +__all__ = ['FunctionContext', 'ScalarFunction', 'udf'] + + +class FunctionContext(object): + """ + Used to obtain global runtime information about the context in which the + user-defined function is executed. The information includes the metric group, + and global job parameters, etc. + """ + pass + + +class UserDefinedFunction(object): + """ + Base interface for user-defined function. + """ + __metaclass__ = ABCMeta Review comment: It's a best practice to declare the ABCMeta if it's an abstract class in Python. Quoted from [StackOverFlow](https://stackoverflow.com/questions/3570796/why-use-abstract-base-classes-in-python): "A handy feature of ABCs is that if you don't implement all necessary methods (and properties) you get an error upon instantiation, rather than an AttributeError, potentially much later, when you actually try to use the missing method.". I'll add a test case. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
