215 lines
8.0 KiB
Python
215 lines
8.0 KiB
Python
import sqlite3 as sql
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from dataclasses import Field, asdict, dataclass
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from typing import List, Dict, Optional, Callable, Any
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def _convert_type(type_: Optional[type], type_overload: Dict[Optional[type], str]) -> str:
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"""
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Given a Python type, return the str name of its
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SQLlite equivalent.
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:param type_: A Python type, or None.
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:param type_overload: A type table to overload the custom type table.
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:return: The str name of the sql type.
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>>> _convert_type(int)
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"INTEGER"
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"""
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try:
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return type_overload[type_]
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except KeyError:
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raise TypeError("Requested type not in the default or overloaded type table.")
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def _convert_sql_format(value: Any) -> str:
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"""
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Given a Python value, convert to string representation
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of the equivalent SQL datatype.
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:param value: A value, ie: a literal, a variable etc.
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:return: The string representation of the SQL equivalent.
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>>> _convert_sql_format(1)
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"1"
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>>> _convert_sql_format("John Smith")
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'"John Smith"'
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"""
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if isinstance(value, str):
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return f'"{value}"'
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else:
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return str(value)
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def _get_default(default_object: object, type_overload: Dict[Optional[type], str]) -> str:
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"""
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Check if the field's default object is filled,
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if filled return the string to be put in the,
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database.
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:param default_object: The default field of the field.
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:param type_overload: Type overload table.
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:return: The string to be put on the table statement,
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empty string if no string is necessary.
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"""
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if type(default_object) in type_overload:
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if isinstance(default_object, str):
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return f' DEFAULT "{default_object}"'
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else:
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return f" DEFAULT {str(default_object)}"
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return ""
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def _create_table(class_: type, cursor: sql.Cursor, type_overload: Dict[Optional[type], str]) -> None:
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"""
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Create the table for a specific dataclass given
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:param class_: A dataclass.
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:param cursor: Current cursor instance.
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:param type_overload: Overload the Python -> SQLDatatype table
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with a custom table, this is that custom table.
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:return: None.
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"""
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fields: List[Field] = [class_.__dataclass_fields__[key] for
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key in class_.__dataclass_fields__.keys()]
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fields.sort(key=lambda field: field.name) # Since dictionaries *may* be unsorted.
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sql_fields = ', '.join(f"{field.name} {_convert_type(field.type, type_overload)}"
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f"{_get_default(field.default, type_overload)}" for field in fields)
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sql_fields = "obj_id INTEGER PRIMARY KEY AUTOINCREMENT, " + sql_fields
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cursor.execute(f"CREATE TABLE IF NOT EXISTS {class_.__name__.lower()} ({sql_fields});")
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def _create_entry(self) -> None:
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"""
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Given an object, create the entry for the object. As a side-effect,
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this will set the object_id attribute of the object to the unique
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id of the entry.
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:param self: Instance of the object.
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:return: None.
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"""
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with sql.connect(getattr(self, "db_path")) as con:
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cur: sql.Cursor = con.cursor()
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table_name: str = self.__class__.__name__.lower()
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kv_pairs = [item for item in asdict(self).items()]
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kv_pairs.sort(key=lambda item: item[0]) # Sort by the name of the fields.
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cur.execute(f"INSERT INTO {table_name}("
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f"{', '.join(item[0] for item in kv_pairs)})"
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f" VALUES ({', '.join(_convert_sql_format(item[1]) for item in kv_pairs)});")
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self.__setattr__("obj_id", cur.lastrowid)
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con.commit()
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def _remove_entry(self) -> None:
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"""
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Remove the object's record in the underlying database.
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:param self: self instance.
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:return: None.
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"""
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with sql.connect(getattr(self, "db_path")) as con:
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cur: sql.Cursor = con.cursor()
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cur.execute(f"DELETE FROM {self.__class__.__name__.lower()} WHERE obj_id = {self.obj_id}")
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con.commit()
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def datalite(db_path: str, type_overload: Optional[Dict[Optional[type], str]] = None,
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*args, **kwargs) -> Callable:
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def decorator(dataclass_: type, *args_i, **kwargs_i):
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type_table: Dict[Optional[type], str] = {None: "NULL", int: "INTEGER", float: "REAL",
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str: "TEXT", bytes: "BLOB"}
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if type_overload is not None:
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type_table.update(type_overload)
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with sql.connect(db_path) as con:
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cur: sql.Cursor = con.cursor()
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_create_table(dataclass_, cur, type_table)
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setattr(dataclass_, 'db_path', db_path) # We add the path of the database to class itself.
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dataclass_.create_entry = _create_entry
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return dataclass_
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return decorator
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def is_fetchable(class_: type, obj_id: int) -> bool:
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"""
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Check if a record is fetchable given its obj_id and
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class_ type.
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:param class_: Class type of the object.
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:param obj_id: Unique obj_id of the object.
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:return: If the object is fetchable.
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"""
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with sql.connect(getattr(class_, 'db_path')) as con:
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cur: sql.Cursor = con.cursor()
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try:
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cur.execute(f"SELECT 1 FROM {class_.__name__.lower()} WHERE obj_id = {obj_id};")
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except sql.OperationalError:
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raise KeyError(f"Table {class_.__name__.lower()} does not exist.")
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return bool(cur.fetchall())
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def _get_table_cols(cur: sql.Cursor, table_name: str) -> List[str]:
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"""
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Get the column data of a table.
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:param cur: Cursor in database.
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:param table_name: Name of the table.
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:return: the information about columns.
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"""
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cur.execute(f"PRAGMA table_info({table_name});")
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return [row_info[1] for row_info in cur.fetchall()][1:]
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def fetch_from(class_: type, obj_id: int) -> Any:
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"""
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Fetch a class_ type variable from its bound db.
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:param class_: Class to fetch.
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:param obj_id: Unique object id of the class.
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:return: The object whose data is taken from the database.
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"""
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table_name = class_.__name__.lower()
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if not is_fetchable(class_, obj_id):
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raise KeyError(f"An object with the id {obj_id} in table {table_name} does not exist."
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f"or is otherwise unable to be fetched.")
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with sql.connect(getattr(class_, 'db_path')) as con:
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cur: sql.Cursor = con.cursor()
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cur.execute(f"SELECT * FROM {class_.__name__.lower()} WHERE obj_id = {obj_id};") # Guaranteed to work.
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field_values: List[str] = list(cur.fetchone())[1:]
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field_names: List[str] = _get_table_cols(cur, class_.__name__.lower())
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kwargs = dict(zip(field_names, field_values))
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obj = class_(**kwargs)
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setattr(obj, "obj_id", obj_id)
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return obj
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def fetch_range(class_: type, range_: range) -> tuple:
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"""
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Fetch the records in a given range of object ids.
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:param class_: Class of the records.
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:param range_: Range of the object ids.
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:return: A tuple of class_ type objects whose values
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come from the class_' bound database.
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"""
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return tuple(fetch_from(class_, obj_id) for obj_id in range_ if is_fetchable(class_, obj_id))
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def fetch_all(class_: type) -> tuple:
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"""
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Fetchall the records in the bound database.
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:param class_: Class of the records.
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:return: All the records of type class_ in
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the bound database as a tuple.
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"""
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try:
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db_path = getattr(class_, 'db_path')
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except AttributeError:
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raise TypeError("Given class is not decorated with datalite.")
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with sql.connect(db_path) as con:
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cur: sql.Cursor = con.cursor()
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try:
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cur.execute(f"SELECT * FROM {class_.__name__.lower()}")
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except sql.OperationalError:
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raise TypeError(f"No record of type {class_.__name__.lower()}")
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records = cur.fetchall()
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field_names: List[str] = _get_table_cols(cur, class_.__name__.lower())
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objects: List[class_] = []
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for record in records:
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kwargs = dict(zip(field_names, record[1:]))
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obj_id = record[0]
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obj = class_(**kwargs)
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setattr(obj, "obj_id", obj_id)
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objects.append(obj)
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return tuple(objects)
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