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#!/usr/bin/env python3
import pickle
from typing import Any, Mapping
import file_utils
class PersistentState(object):
"""
An object that behaves like a persistent hash map; it can be
accessed to store key-value pairs but also saved to disk and read
back from disk easily.
"""
def __init__(self, filename: str, *, max_age_sec: int = None):
self.filename = filename
if file_utils.does_file_exist(self.filename):
if max_age_sec is not None:
age = file_utils.get_file_mtime_age_seconds(self.filename)
if age < max_age_sec:
self.state = self.load()
else:
self.state = {}
else:
self.state = self.load()
else:
self.state = {}
def __getitem__(self, key: str) -> Any:
return self.state.get(key, "")
def __setitem__(self, key: str, value: Any):
self.state[key] = value
def __delitem__(self, key: str):
del self.state[key]
def __iter__(self):
return iter(self.state)
def __len__(self):
return len(self.state)
def save(self) -> None:
with open(self.filename, 'wb') as f:
pickle.dump(self.state, f, pickle.HIGHEST_PROTOCOL)
def load(self) -> Mapping[str, Any]:
with open(self.filename, 'rb') as f:
return(pickle.load(f))
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