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memoize_decorator.py
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memoize_decorator.py
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from asyncio import Lock as AsyncLock
from atools.decorator_mixin import Decoratee, DecoratorMixin, Fn
from collections import deque, ChainMap, OrderedDict
from dataclasses import dataclass, field, InitVar
from datetime import timedelta
import inspect
from time import time
from threading import Lock as SyncLock
from typing import Any, Optional, Union
class _MemoZeroValue:
pass
@dataclass
class _MemoReturnState:
called: bool = False
raised: bool = False
_value: Any = _MemoZeroValue
@property
def value(self) -> Any:
assert self._value is not _MemoZeroValue
return self._value
@value.setter
def value(self, value: Any) -> None:
self._value = value
@dataclass(frozen=True)
class _Memo:
fn: Fn
expire_time: Optional[float]
lock: Union[AsyncLock, SyncLock] = field(init=False)
memo_return_state: _MemoReturnState = field(init=False, default_factory=_MemoReturnState)
def __post_init__(self) -> None:
if inspect.iscoroutinefunction(self.fn):
object.__setattr__(self, 'lock', AsyncLock())
else:
object.__setattr__(self, 'lock', SyncLock())
class _MemoizeState:
def __init__(
self,
fn: Fn,
*,
size: Optional[int] = None,
duration: Optional[Union[int, timedelta]] = None,
) -> None:
self._fn = fn
self._size = size
self._duration = duration.total_seconds() if isinstance(duration, timedelta) else duration
assert self._size is None or self._size > 0
assert self._duration is None or self._duration > 0
if self._duration is None:
self._expire_order = None
else:
self._expire_order = OrderedDict()
self._memos: OrderedDict = OrderedDict()
self._default_kwargs: OrderedDict = OrderedDict([
(k, v.default) for k, v in inspect.signature(self._fn).parameters.items()
])
def __len__(self) -> int:
return len(self._memos)
def reset(self) -> None:
self._memos = OrderedDict()
self._expire_order = deque() if self._expire_order is not None else None
def make_key(self, *args, **kwargs) -> int:
"""Returns all params (args, kwargs, and missing default kwargs) for function as kwargs."""
args_as_kwargs = {}
for k, v in zip(self._default_kwargs, args):
args_as_kwargs[k] = v
return hash(tuple(ChainMap(args_as_kwargs, kwargs, self._default_kwargs).values()))
def get_memo(self, key: int) -> _Memo:
try:
memo = self._memos[key] = self._memos.pop(key)
if self._duration is not None and memo.expire_time < time():
self._expire_order.pop(key)
raise ValueError('value expired')
except (KeyError, ValueError):
if self._duration is None:
expire_time = None
else:
expire_time = time() + self._duration
self._expire_order[key] = ...
memo = self._memos[key] = _Memo(self._fn, expire_time=expire_time)
return memo
def expire_one_memo(self) -> None:
if self._expire_order is not None and \
len(self._expire_order) > 0 and \
self._memos[next(iter(self._expire_order))].expire_time < time():
self._memos.pop(self._expire_order.popitem(last=False)[0])
elif self._size is not None and self._size < len(self._memos):
self._memos.popitem(last=False)
_all_decorators = set()
@dataclass(frozen=True)
class _MemoizeAsync:
fn: InitVar[Fn]
size: InitVar[Optional[int]] = None
duration: InitVar[Optional[Union[int, timedelta]]] = None
_state: _MemoizeState = field(init=False)
def __post_init__(
self, fn: Fn, size: Optional[int], duration: Optional[Union[int, timedelta]]
) -> None:
object.__setattr__(self, '_state', _MemoizeState(fn=fn, size=size, duration=duration))
_all_decorators.add(self)
async def __call__(self, *args, **kwargs) -> Any:
key = self._state.make_key(*args, **kwargs)
memo = self._state.get_memo(key)
self._state.expire_one_memo()
async with memo.lock:
if not memo.memo_return_state.called:
memo.memo_return_state.called = True
try:
memo.memo_return_state.value = await memo.fn(*args, **kwargs)
except Exception as e:
memo.memo_return_state.raised = True
memo.memo_return_state.value = e
if memo.memo_return_state.raised:
raise memo.memo_return_state.value
else:
return memo.memo_return_state.value
def __len__(self) -> int:
return len(self._state)
def reset(self) -> None:
self._state.reset()
_memoize_async = type('memoize', (_MemoizeAsync,), {})
@dataclass(frozen=True)
class _MemoizeSync:
fn: InitVar[Fn]
size: InitVar[Optional[int]] = None
duration: InitVar[Optional[Union[int, timedelta]]] = None
_state: _MemoizeState = field(init=False)
_sync_lock: SyncLock = field(init=False, default_factory=SyncLock)
def __post_init__(
self, fn: Fn, size: Optional[int], duration: Optional[Union[int, timedelta]]
) -> None:
object.__setattr__(self, '_state', _MemoizeState(fn=fn, size=size, duration=duration))
_all_decorators.add(self)
def __call__(self, *args, **kwargs) -> Any:
key = self._state.make_key(*args, **kwargs)
with self._sync_lock:
memo = self._state.get_memo(key)
self._state.expire_one_memo()
with memo.lock:
if not memo.memo_return_state.called:
memo.memo_return_state.called = True
try:
memo.memo_return_state.value = memo.fn(*args, **kwargs)
except Exception as e:
memo.memo_return_state.raised = True
memo.memo_return_state.value = e
if memo.memo_return_state.raised:
raise memo.memo_return_state.value
else:
return memo.memo_return_state.value
def __len__(self) -> int:
return len(self._state)
def reset(self) -> None:
with self._sync_lock:
self._state.reset()
_memoize_sync = type('memoize', (_MemoizeSync,), {})
class _Memoize:
"""Decorates a function call and caches return value for given inputs.
If 'size' is provided, memoize will only retain up to 'size' return values.
If 'expire' is provided, memoize will only retain return values for up to 'expire' duration.
Examples:
- Body will run once for unique input 'bar' and result is cached.
@memoize
def foo(bar) -> Any: ...
foo(1) # Function actually called. Result cached.
foo(1) # Function not called. Previously-cached result returned.
foo(2) # Function actually called. Result cached.
- Same as above, but async.
@memoize
async def foo(bar) -> Any: ...
# Concurrent calls from the same thread are safe. Only one call is generated. The
other nine calls in this example wait for the result.
await asyncio.gather(*[foo(1) for _ in range(10)])
- Classes may be memoized.
@memoize
Class Foo:
def init(self, _): ...
Foo(1) # Instance is actually created.
Foo(1) # Instance not created. Previously-cached instance returned.
Foo(2) # Instance is actually created.
- Calls to foo(1), foo(bar=1), and foo(1, baz='baz') are equivalent and only cached once
@memoize
def foo(bar, baz='baz'): ...
- Only 10 items are cached. Acts as an LRU.
@memoize(size=2)
def foo(bar) -> Any: ...
foo(1) # LRU cache order [foo(1)]
foo(2) # LRU cache order [foo(1), foo(2)]
foo(1) # LRU cache order [foo(2), foo(1)]
foo(3) # LRU cache order [foo(1), foo(3)], foo(2) is evicted to keep cache size at 2
- Items are evicted after 1 minute.
@memoize(duration=datetime.timedelta(minutes=1))
def foo(bar) -> Any: ...
foo(1) # Function actually called. Result cached.
foo(1) # Function not called. Previously-cached result returned.
sleep(61)
foo(1) # Function actually called. Previously-cached result was too old.
- Memoize can be explicitly reset through the function's 'memoize' attribute
@memoize
def foo(bar) -> Any: ...
foo(1) # Function actually called. Result cached.
foo(1) # Function not called. Previously-cached result returned.
foo.memoize.reset()
foo(1) # Function actually called. Cache was emptied.
- Current cache size can be accessed through the function's 'memoize' attribute
@memoize
def foo(bar) -> Any: ...
foo(1)
foo(2)
len(foo.memoize) # returns 2
- Properties can be memoized
Class Foo:
@property
@memoize
def bar(self, baz): -> Any: ...
a = Foo()
a.bar # Function actually called. Result cached.
a.bar # Function not called. Previously-cached result returned.
b = Foo() # Memoize uses 'self' parameter in hash. 'b' does not share returns with 'a'
b.bar # Function actually called. Result cached.
b.bar # Function not called. Previously-cached result returned.
- Be careful with eviction on methods.
Class Foo:
@memoize(size=1)
def foo(self): -> Any: ...
a, b = Foo(), Foo()
a.bar(1) # LRU cache order [Foo.bar(a)]
b.bar(1) # LRU cache order [Foo.bar(b)], Foo.bar(a) is evicted
a.bar(1) # Foo.bar(a, 1) is actually called cached and again.
"""
_all_decorators = set()
def __new__(
cls,
decoratee: Decoratee,
*,
size: Optional[int] = None,
duration: Optional[Union[int, timedelta]] = None,
):
if inspect.iscoroutinefunction(decoratee):
return _memoize_async(decoratee, size=size, duration=duration)
elif not inspect.isclass(decoratee):
return _memoize_sync(decoratee, size=size, duration=duration)
elif inspect.isclass(decoratee):
class WrappedMeta(type(decoratee)):
# noinspection PyMethodParameters
@memoize
def __call__(cls, *args, **kwargs):
return super().__call__(*args, **kwargs)
class Wrapped(decoratee, metaclass=WrappedMeta):
pass
return type(decoratee.__name__, (Wrapped,), {'__doc__': decoratee.__doc__})
@staticmethod
def reset_all() -> None:
for decorator in _all_decorators:
decorator.reset()
memoize = type('memoize', (DecoratorMixin, _Memoize), {})