#!/usr/bin/env python
# cardinal_pythonlib/sqlalchemy/table_identity.py
"""
===============================================================================
Original code copyright (C) 2009-2022 Rudolf Cardinal (rudolf@pobox.com).
This file is part of cardinal_pythonlib.
Licensed 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
https://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.
===============================================================================
**Class to refer to database tables either by name or by SQLAlchemy Table
object.**
"""
from sqlalchemy.sql.schema import MetaData, Table
from cardinal_pythonlib.logs import get_brace_style_log_with_null_handler
log = get_brace_style_log_with_null_handler(__name__)
# =============================================================================
# TableIdentity
# =============================================================================
[docs]class TableIdentity(object):
"""
Convenient way of passing around SQLAlchemy :class:`Table` objects when you
might know either either its name or the :class:`Table` object itself.
"""
def __init__(
self,
tablename: str = None,
table: Table = None,
metadata: MetaData = None,
) -> None:
"""
Initialize with either ``tablename`` or ``table``, not both.
Args:
tablename: string name of the table
table: SQLAlchemy :class:`Table` object
metadata: optional :class:`MetaData` object
"""
assert table is not None or tablename, "No table information provided"
assert not (
tablename and table is not None
), "Specify either table or tablename, not both"
self._table = table
self._tablename = tablename
self._metadata = metadata
def __str__(self) -> str:
return self.tablename
def __repr__(self) -> str:
return (
f"TableIdentity(table={self._table!r}, "
f"tablename={self._tablename!r}, metadata={self._metadata!r}"
)
@property
def table(self) -> Table:
"""
Returns a SQLAlchemy :class:`Table` object. This is either the
:class:`Table` object that was used for initialization, or one that
was constructed from the ``tablename`` plus the ``metadata``.
"""
if self._table is not None:
return self._table
assert self._metadata, (
"Must specify metadata (in constructor or via set_metadata()/"
"set_metadata_if_none() before you can get a Table from a "
"tablename"
)
for table in self._metadata.tables.values(): # type: Table
if table.name == self._tablename:
return table
raise ValueError(
f"No table named {self._tablename!r} is present in the metadata"
)
@property
def tablename(self) -> str:
"""
Returns the string name of the table.
"""
if self._tablename:
return self._tablename
return self.table.name