Added "Decorators__examples/decorator_method_class__with_shelve.py"

Author: gil9red

Diff for: Decorators__examples/decorator_method_class__with_shelve.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+__author__ = "ipetrash"
+
+
+import shelve
+import functools
+
+from pathlib import Path
+from typing import Any
+
+
+DIR: Path = Path(__file__).resolve().parent
+DIR_DB: Path = DIR / "databases"
+DB_FILE_NAME: Path = DIR_DB / "db.shelve"
+
+
+DIR_DB.mkdir(parents=True, exist_ok=True)
+
+
+class DB:
+    db_name: str = str(DB_FILE_NAME)
+
+    def __init__(self):
+        self.db: shelve.Shelf | None = None
+
+    def session(*decorator_args, **decorator_kwargs):
+        def actual_decorator(func):
+            @functools.wraps(func)
+            def wrapped(self, *args, **kwargs):
+                has_db: bool = self.db is not None
+                try:
+                    if not has_db:
+                        self.db = shelve.open(self.db_name, writeback=True)
+                    return func(self, *args, **kwargs)
+                finally:
+                    if not has_db and self.db is not None:
+                        self.db.close()
+                        self.db = None
+
+            return wrapped
+
+        return actual_decorator
+
+    @session()
+    def get_value(self, name: str, default: Any = None) -> Any:
+        if not name:
+            return dict(self.db)
+
+        if name not in self.db:
+            return default
+        return self.db.get(name)
+
+    @session()
+    def set_value(self, name: str, value: Any):
+        self.db[name] = value
+
+    def inc_value(self, name: str) -> int:
+        value = self.get_value(name, default=0)
+        value += 1
+        self.set_value(name, value)
+        return value
+
+
+if __name__ == "__main__":
+    db = DB()
+    print("name", db.get_value("name"))
+
+    db.set_value("name", 123)
+
+    users: dict[str, dict[str, Any]] = db.get_value("users", default=dict())
+    print("users", users)
+    if not users:
+        users["Foo"] = dict(name="Foo", age=12)
+        users["Bar"] = dict(name="Bar", age=12)
+        db.set_value("users", users)
+
+    counter: dict[str, int] = db.get_value("counter", default=dict())
+    print("counter", counter)
+    if "value" not in counter:
+        counter["value"] = 0
+    counter["value"] += 1
+    db.set_value("counter", counter)
+
+    print([db.inc_value("age") for _ in range(3)])
+
+    print(dict(db.get_value("")))