/
config.py
82 lines (66 loc) · 2.23 KB
/
config.py
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import contextlib
import os
import sys
if sys.version_info >= (3, 7):
_USES_CONTEXT_VARS = True
import contextvars
else:
_USES_CONTEXT_VARS = False
class _Config:
"""Main configuration singleton object.
In Python 3.7+, it uses contextvars to enable async/thread-safe.
"""
_instance = None
def __new__(cls, *args, **kwargs):
if not cls._instance:
cls._instance = object.__new__(cls)
return cls._instance
raise ValueError("Config is a singleton object.")
def _make_var(self, name, default):
if _USES_CONTEXT_VARS:
var = contextvars.ContextVar(name, default=default)
else:
var = default
setattr(self, name, var)
def _get_value(self, name):
var = getattr(self, name)
if _USES_CONTEXT_VARS:
return var.get()
return var
def _set_value(self, name, value) -> None:
if _USES_CONTEXT_VARS:
var = getattr(self, name)
return var.set(value)
else:
setattr(self, name, value)
@contextlib.contextmanager
def _change_value(self, name, value):
if _USES_CONTEXT_VARS:
token = getattr(self, name).set(value)
try:
yield
finally:
getattr(self, name).reset(token)
else:
original_value = getattr(self, name)
try:
setattr(self, name, value)
yield
finally:
setattr(self, name, original_value)
def __init__(self):
self._make_var("_free_arithmetics", os.environ.get("PHYST_FREE_ARITHMETICS", "0") == "1")
@property
def free_arithmetics(self) -> bool:
"""Whether to allow arithmetic operations regardless of their reasonability."""
return self._get_value("_free_arithmetics")
@free_arithmetics.setter
def free_arithmetics(self, value: bool):
self._set_value("_free_arithmetics", value)
@contextlib.contextmanager
def enable_free_arithmetics(self, value: bool = True):
"""Temporarily allow/disallow benevolent arithmetics rules."""
with self._change_value("_free_arithmetics", value):
yield
config = _Config()
del os