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datacolumn.py
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datacolumn.py
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# ******************************************************************************************************
# datacolumn.py - Gbtc
#
# Copyright © 2022, Grid Protection Alliance. All Rights Reserved.
#
# Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See
# the NOTICE file distributed with this work for additional information regarding copyright ownership.
# The GPA licenses this file to you under the MIT License (MIT), the "License"; you may not use this
# file except in compliance with the License. You may obtain a copy of the License at:
#
# http://opensource.org/licenses/MIT
#
# Unless agreed to in writing, the subject software distributed under the License is distributed on an
# "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the
# License for the specific language governing permissions and limitations.
#
# Code Modification History:
# ----------------------------------------------------------------------------------------------------
# 08/26/2022 - J. Ritchie Carroll
# Generated original version of source code.
#
# ******************************************************************************************************
from __future__ import annotations
from gsf import Empty, normalize_enumname
from .datatype import DataType
from typing import TYPE_CHECKING
if TYPE_CHECKING:
from .datatable import DataTable
class DataColumn:
"""
Represents a column, i.e., a field, in a `DataTable` defining a name and a data type.
Data columns can also be computed where its value would be derived from other columns and
functions (https://sttp.github.io/documentation/filter-expressions/) defined in an expression.
"""
def __init__(self,
parent: DataTable,
name: str,
datatype: DataType,
expression: str = ...
):
"""
Creates a new `DataColumn`.
"""
self._parent = parent
self._name = name
self._datatype = datatype
self._expression = Empty.STRING if expression is ... or expression is None else expression
self._computed = len(self._expression) > 0
self._index = -1
@property
def parent(self) -> DataTable:
"""
Gets the parent `DataTable` of the `DataColumn`.
"""
return self._parent
@property
def name(self) -> str:
"""
Gets the column name of the `DataColumn`.
"""
return self._name
@property
def datatype(self) -> DataType:
"""
Gets the column `DataType` enumeration value of the `DataColumn`.
"""
return self._datatype
@property
def expression(self) -> str:
"""
Gets the column expression value of the `DataColumn`, if any.
"""
return self._expression
@property
def computed(self) -> bool:
"""
Gets a flag that determines if the `DataColumn` is a computed value,
i.e., has a defined expression.
"""
return self._computed
@property
def index(self) -> int:
"""
Gets the index of the `DataColumn` within its parent `DataTable` columns collection.
"""
return self._index
def __repr__(self):
datatype = normalize_enumname(self._datatype)
if self._computed:
datatype = f"Computed {datatype}"
return f"{self._name} ({datatype})"