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Use locking when creating singleton

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This commit is contained in:
Keith Edmunds 2025-01-27 14:25:04 +00:00
parent d3a709642b
commit 4927f237ab
1 changed files with 10 additions and 3 deletions
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13
app/classes.py
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@ -1,9 +1,10 @@
# Standard library imports # Standard library imports
from __future__ import annotations from __future__ import annotations
from dataclasses import dataclass, field from dataclasses import dataclass
from enum import auto, Enum from enum import auto, Enum
import functools import functools
import threading
from typing import NamedTuple from typing import NamedTuple
# Third party imports # Third party imports
@ -34,12 +35,18 @@ def singleton(cls):
""" """
Make a class a Singleton class (see Make a class a Singleton class (see
https://realpython.com/primer-on-python-decorators/#creating-singletons) https://realpython.com/primer-on-python-decorators/#creating-singletons)
Added locking.
""" """
lock = threading.Lock()
@functools.wraps(cls) @functools.wraps(cls)
def wrapper_singleton(*args, **kwargs): def wrapper_singleton(*args, **kwargs):
if not wrapper_singleton.instance: if wrapper_singleton.instance is None:
wrapper_singleton.instance = cls(*args, **kwargs) with lock:
if wrapper_singleton.instance is None: # Check still None
wrapper_singleton.instance = cls(*args, **kwargs)
return wrapper_singleton.instance return wrapper_singleton.instance
wrapper_singleton.instance = None wrapper_singleton.instance = None