xinbinhuang commented on a change in pull request #3407: URL: https://github.com/apache/iceberg/pull/3407#discussion_r744180241
########## File path: python/src/iceberg/schema.py ########## @@ -0,0 +1,67 @@ +# 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. + +from .types import StructType, Type, NestedField + + +class Schema(object): + alias_to_id: dict = None + id_to_field = {} + name_to_id: dict = None + lowercase_name_to_id: dict = None Review comment: It seems that here is declaring mutable variables as class attributes. This can be problematic because class attributes are mutable and persist across the same python session. i.e. ```python class Spec: id: str = None name: str = None spec1 = Spec() spec2 = Spec() assert(spec1.id is None) # change class variable from an instance spec2.__class__.id = "spec2_id" assert(spec1.id == "spec2_id") assert(Spec.id == "spec2_id") spec3 = Spec() assert(spec3.id == "spec2_id") Spec.id = "class_spec_id" assert(spec1.id == "class_spec_id") assert(spec2.id == "class_spec_id") assert(spec3.id == "class_spec_id") ``` In the above example, an instance can change the class variable and it affects all other current and future instances. This can lead to surprising behavior. To have instance scope only variables, we can put them inside the init without exposing them to the signature. i.e. ```python def __init__(self, struct: StructType, schema_id: int, identifier_field_ids: [int]): self._struct = struct self._schema_id = schema_id self._identifier_field_ids = identifier_field_ids # not initialized by the user externally self.alias_to_id: dict = None self.id_to_field = {} self.name_to_id: dict = None self.lowercase_name_to_id: dict = None ``` -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
